Saponification reaction to make soap ; Hydrolysis promoted by alkali ester.

Saponification reaction to make soap can be said to be hydrolysis promoted by alkali ester.

Fats and oils + NaOH ⇒ soap + glycerin

There is no water in the chemical reaction formula.



So you can use an extremely thick caustic soda solution.

The saturated concentration of caustic soda was 19 mol / liter
Seemingly,
You can solute by 100 grams of NaOH in 100 grams of water.
In terms of molar ratio,
It is saturated at about 1: 3 with NaOH: H 2 O,
We use 1: 5 molar ratio (1: 2 by weight ratio) for soap making.

Now,

When oil and fat and caustic soda aqueous solution are heated slightly and mixed, the reaction proceeds naturally.

Chemical reaction,
If the free energy is minus, proceed.

Free energy is Enthalpy (minus for exothermic reactions) - Absolute temperature * Entropy (plus if clutter increases)

In response to this relationship, reactions that increase exothermic reactions or disorder will progress naturally.

Here,

In the saponification reaction, the calorific value is small. It seems to be about 40 KJ / mol.

If the amount of fat or oil of about 500 grams is 1 mole,

Because it is 40 kJ, it is about 10 kilocalories.

It's heat enough to raise 1000 grams of water by 10 degrees.

Because it is not 1 kilogram of fats and oils and alkali, it is calculated to rise by 10 ℃ or more with fever.
However, it is easy to cool down when the surroundings are cold, insulation is said to be important.

Also the clutter has not changed so much.

that is
1) Nucleophilic attack of oil promoted to base by water is caused.

2) One of the double bonds between carbon and oxygen of the ester is broken.

3) It goes through a state where there are four bonds centered on carbon.

4) The oxygen of the ester and the glycerin moiety are eliminated and a double bond between oxygen is born again and a carboxylic acid is generated.

5) Hydrogen is transferred from carboxylic acid to glycerin moiety.

6) Carboxylic acid makes salt with sodium, glycerin is completed.


Here, since 1) to 4) are equilibrium reactions, increasing the temperature raises the reaction rate.


And 5) When the sodium salt of 6) is made, it is soap, it does not react nucleophilically,

Glycerin is a very weak acid, while carboxylic acid is an acid,

Only relatively strong acid carboxylates are preferentially made.


And since the soap never returns again, the reaction naturally proceeds irreversibly.



For reaction rate,
The process of increasing the contact area where the first water and oil mix,

Followed by saponification progress.

In particular, the reaction in the second half proceeds at such a rate that the half life is constant.

The reaction rate gradually declines as the concentration decreases.

The chemistry of saponification and Reaction rate

While studying the chemistry of saponification, I noticed the point of reaction rate.

dx / dt = k (a - x) (b - X) = v

a and b are the concentrations of the starting materials, X is the soap concentration, and t is the reaction time.
That is the expression. The reaction velocity v slows as the reaction progresses.

The way of making soap gradually progresses at a stroke in the beginning, gradually, and finally it is finished again slowly.

As shown in the figure, the soap quickly rises on the way,
At that time the reaction rate will slow down at a stretch.


In an experiment at a certain university, they measured the percentage of soap produced by changing the temperature to find the reaction rate coefficient and the activation energy of the reaction.


The reaction progresses in a so-called exponential fashion.

Although the reaction rate is fast at first, the soap of the reaction product is small.

There is a point where a lot of soap can proceed rapidly exponentially from a certain point.

Subsequently, the reaction rate rapidly slowed down, slowly stopped,

Comprehension is completed so that it can be matured over a long period of time.

That is such a reaction.



In order to make saponification faster,

1) Increasing the concentration,

2) Increase the temperature

3) Stir well

4) Put the catalyst



Regardless of oil,

If caustic soda is not dissolved in water, it become small ball and remains unresponsive and it is very dangerous.

Try not to make too caustic soda water.

It is about 30% weight concentration.

30 grams of caustic soda will be about the maximum for 70 grams of water.



Increasing the temperature increases the movement of the molecule and has the same effect as stirring microscopically.

If it stirs, the number of times caustic soda and oil and fat molecules meet many times increases, The reaction speed increases.

However, when raised to 60 ° C or higher, there are decomposition of fats and oils and oxidation reactions,
Temperature rise too much is caution.


Besides that, as a catalyst,Alcohol addition etc. are known.

This is a method to increase the speed by adding things that have the property that the reaction tends to advance easily.



Given the reaction speed in earnest,

They compare the two types of making temperature 40 degrees, 60 degrees.

They measure the amount of alkali in unfinished soap made every few minutes by titration.

From the amount of citric acid until neutralization by adding the same concentration of citric acid,
Estimate the amount of unreacted alkali.

The ester concentration, alkali concentration and reaction rate constant k at time t are determined and are summarized in the table.


If log k is taken on the vertical axis and 1000 / T (temperature) is taken on the horizontal axis, there is a linear relationship.


The reaction rate coefficient increases as the temperature rises.

In the saponification of acetic acid esters,

The activation energy Ea of saponification is approximately Ea=59.1 kJ / mol

It seems to be about.

The reaction rate coefficient from room temperature to 50 ° C.,

20 ° C ; k '= A exp (- Ea / 293 R) = 0.002

30 ° C ; k '= A exp (- Ea / 303 R) = 0.005

40 ° C ; k '= A exp (- Ea / 313 R) = 0.010

50 ° C ; k '= A exp (- Ea / 323 R) = 0.022



In other words, at 40 ° C and 50 ° C, the reaction speed increases by 2 times as it goes up by 10 °.

The greater the activation energy, the greater the effect when the temperature goes up.

Here,
In saponification of palm oil,

Ea = 3-5 kcal / mol

The value has come out.

This is,

1 J = about 0.239 Calculated by cal (calories)

4 kcal = 16.7 kJ / mol.


You can calculate 14.1 kcal for Ea = 59.1 kJ.

In other words, the activation energy of palm oil is lower than that of acetic acid ester,

The reaction rate is slow.

(The above article is based on http: // 326.nobody.jp/ouka1/reaction_rate.htm)

(The above article also refers to kurepo.clib.kindai.ac.jp / modules / xoonips / download.php? File_id = 8106)

 In the case of Ea = 17 kJ / mol,

K 40 / K 50 = exp {-17 / 8.31 * (1/323 - 1/313)}
= About 1.2
(The above article also refers to http://pub.maruzen.co.jp/book_magazine/support/cgbukka_pdf/11.pdf)


At 40 ° C and 50 ° C the reaction rate is calculated to be about 1.2 times.

(The following description is based on " http://kumaguma-soap.blog.so-net.ne.jp/2008-09-06)

Iodine value and saponification rate constant (McBain and Kawakami, J. Phys. Chem. Soc., 1929, 2185)



The greater the speed constant, the faster the reaction.
The larger the iodine value is, the slower the reaction is shown.



Iodine value is a value that shows how much unsaturated bonds are in fat and oil.

That is, oils with many unsaturated fatty acids can be considered to be slow reactions.

Many vegetable fats such as beef tallow, lard, palm oil and the like have low iodine value,
Saponification speed is fast.



Conversely, those with high iodine values ​​such as soybean oil and olive oil are many in unsaturated fatty acids,
The degradation reaction rate is slow.





As described above, not only reaction conditions such as temperature,

There are also speed differences depending on the type of oil.

Temperature and iodine value of oil are important factors.



Besides that, rice oil (rice bran oil) contains a few percent of impurities,

For that reason, it is very fast.



Reaction speed will be as above if you organize what you grasp by experience.


Summury

Reaction rate of saponification depends on Temperature, iodine values and catalyst.
High speed on  low  iodine value , low unsaturated fatty acids and high temperature.

Homemade Soap ,food, health and chemistry

Homemade Soap and chemistry

1) What is soap?

There seems to be a recipe of soap more than 5000 years ago. There is a legend that made soap made by chance from ashes and water of fat and tree when flesh of sheep was baked, to complete as a recipe.

1-1) History

In Europe, especially France and Mediterranean side produced by olive oil, the culture of making soap was continued until the 18th century. It has been mainly used for washing clothes and so on.


Characteristics of age soap

Originated in Babylonia (Syria) 2800 BC A mixture of ash and fat

From 9th to 10th century to Spain, Italy Soft soap of charcoal, tallow

12 th century Marseille soap seaweed ash and olive oil

Industrialization of alkaline agents in the 18th century Soda carbonate and fats and oils

Electrolysis method of modern caustic soda method of caking of fat and caustic soda

Ion exchange membrane method of modern caustic soda neutralization method of fatty acid and caustic soda


1-2) History in Japan

In Japan, there was a culture of "Yuami" from before the Warring States Period, washing the body with hot water. At that time, soap was not used. It was transmitted from Europe and was presented to Daimyo, but ordinary people were washing their body with pumice.

1-3) Synthetic soap

A large amount of soap used by soldiers will be needed during the First World War, but as a result of the development of the coal chemical industry in Germany, a synthetic detergent was invented, not enough for natural materials.

1-4) straight chain alkyl

Synthetic detergents containing branched alkyl fats and oils which are difficult to be biodegraded pose a problem and have been improved to straight chain alkyl fats and oils which are easily biodegradable.

1-5) Phosphorus-free

Detergents containing phosphorus caused eutrophication and sludge and red tide. Phosphorus is the nutrition of the plant, but when it flows excessively into the river, a phenomenon occurs in which plankton breeds abnormally and the fish can not live. Therefore, phosphorus-free phosphorus-free detergent was developed. (Top released in 1979)

1-6) Enzyme detergent

Among the improvements in detergents, soaps containing enzymes that break down protein contamination have been released, focusing on the fact that the soil of clothes is protein. Even now, it is becoming mainstream detergent. After that, as the synthetic detergent became more compact, we were able to do the same amount of washing with a small amount.


2) Environment and Chemicals


Household wastewater exceeds industrial and agricultural wastewater. Phosphorus is proceeding with countermeasures such as phosphorus-free detergent. On an industrial scale, recycling is proceeding to recover wastewater and harmful components after detoxification and not to discharge it to the outside. In agriculture, wastewater is the cause of water pollution due to the use of nitrogen, potassium, phosphorus fertilizer and the use of pesticides.

Regarding domestic wastewater, which is the party we are the most from things from the kitchen, followed by soul, bath and laundry. Among them, dirt by disposing and cleaning the food itself is conspicuous. Do not leave it, do not drain easily into water, when washing dishes, you can devise to wipe off dirt and start washing.

The soiling of detergents is estimated at about 12%. It is important that this is not too much detergent. It is to protect the appropriate amount to use against water. Among detergents, we can lower the burden on the environment by paying attention to ingredients. Soap made from grease is made of fatty acid (a kind of carboxylic acid) as a material. On the contrary, many synthetic detergents use sulfonic acid as a material. Sulfonic acid is neutral detergent and is gentle to the skin, but it is said that the load on the environment is high.


2-1) sulfonic acid

The main applications of linear alkylbenzenesulfonic acid are about 80% home laundry detergent, less than 20% cleaning as industrial washing, kitchen and vehicle washing, and it is rarely used for household kitchen detergent It is gone.


Sulfonic acid is a type of acid that is synthesized using sulfuric acid. Because strong acid such as sulfuric acid and strong alkali such as caustic sword are reacting, it does not become alkaline and becomes neutral. We do not make soap scum even in hard water.

Carboxylic acid is derived from normal fats and oils. Fatty acids are a type of carboxylic acid that when reacted with strong alkali can produce alkaline soap.



3) handmade soap

3-1) Material of soap


Soap materials are oil, caustic soda and water. Caustic soda is representative of strong alkali.

Caustic soda is a chemical that is intensely irritating to the skin and mucous membranes, so be careful as it will blind you in your eyes. If it gets in your eyes rinse with plenty of water, it will take the ophthalmologist immediately.


3-2) What is 鹼 化


Reaction that fat and caustic soda reacts to make soap is called crispy. Glycerin is also produced as soap and byproduct.


The amount of soap increases with time. However, it will slowly proceed until a certain period of time, suddenly becoming brittle and solidify. Normally, the viscosity rises in about 1 hour and it solidifies in about 24 hours. And at the end the reaction slowly ends. In addition, it is necessary to neutralize caustic soda with carbon dioxide gas in the air, so it is usually necessary for aging with handmade soap for one or two months.



4) Alkali


4-1) Acid and alkali

Among the properties of water, those with a sour taste are called acids. Citric acid such as apple and lemon is representative. Apart from organic acids, there are gastric juice, hydrochloric acid, sulfuric acid and so on. They found that those with high hydrogen concentration in water recognized the tongue as sour. Therefore, acid is supposed to increase the hydrogen concentration of water.


Alkaline is a null nulled product such as ash which cancels the action of acid. It acts to lower the concentration of oxygen.

The value obtained by measuring acid / alkali with hydrogen concentration is called pH. The pH = 7 is neutral water. A state with very little hydrogen (concentration of -14) is called pH 14. There is a difference of 10 times the hydrogen concentration when the pH is 1 different.


4-2) Water polarity

The reason why oil and water do not mix is ​​because water has polarity. Polarity is related to the fact that molecules of water are electrically biased. Fats and oils are not mixed with water because there is no electric bias. On the other hand, molecules with large electric bias are easily soluble in water. Mainly metal cations and anions that bind them are dissolved in water.





4-2) Sodium hydroxide

Sodium hydroxide is representative of alkali.

Caustic soda melts very much in water. It can be seen that it dissolves more than three times even when compared with similar sodium salt salt, baking soda, etc. This is the polarity strength of sodium hydroxide.

Although sodium bicarbonate is alkaline, it is weak in polarity and hardly soluble in water, so it can not be used for making soap. Sodium salt is polar and soluble in water, but because it is neutral, soap can not be made.

Caustic soda, sodium bicarbonate, salt can be a material to synthesize each other. Industrially, caustic soda is made by electrolyzing salt water.


4-3) pH and color

Many plant dyes change color due to acid alkali change. Anthocyanins, which are representative of plant pigments, are included in red cabbage and hibiscus. Anthocyanin is red when it is acidic, and it changes color from blue to alkaline, and it is used as an indicator to measure pH by using it.

"Red milk" also known as reddish is also discolored a little by alkali. The red soap is an unnatural color. Generally, vivid colors of anthocyanins are discolored on the alkaline side. It can be said that the characteristics of such color are the result of reaction of the dye to pH.


4-4) color

The color is the wavelength of light. It is the length of light wave. The arrangement of the rainbows is arranged in order of the length of the wavelength of the light.

The complementary color of the absorbed light is visible.

Dye changes light absorbed by chemical reaction. The color that can be seen also changes accordingly.





5-1) Sedimentation value


The amount of caustic soda, which is an alkali necessary for sanitization, is organized into recipes and so on as suffering value.

Sulfurization value can be obtained experimentally, but it is calculated from the average molecular weight (ie carbon length).

It is the amount of alkali necessary for saponification where 100% reaction per unit weight of fats and oils progresses. Since oils and fats are mixtures of various fatty acids, their digestibility is different for each fat depending on the mixing ratio. There are values ​​when using potassium as alkali and the value converted into sodium. The potassium digestibility value of olive oil is 191, and 40/56 is 136 in sodium digestion value. It may be written as 0.136 per gram value.


5-2) iodine value


A value obtained by arranging the properties of oils and fats by the amount of iodine reacting to oils and fats.


Among fats and oils, even with the same number of carbons, it can be classified without the presence of double bonds in the carbon skeleton.

Carbon = carbon double bond (unsaturated bond) is highly reactive, it is oxidized and easily deteriorated.

The one with many C = C bonds contained in the oil is consistent with high iodine content.


Something without double bond is called saturation.

One having one double bond is called unsaturated,

Those with two or more double ties are called polyunsaturated.

Iodine value is also an index connecting molecular structure and shape (smooth / solid).


Reaction rate when using this as soap is fast: medium: slow

In other words, an oil containing a lot of unsaturated animal solid fat is low in iodine value and has a principle of accelerating crowding reaction.





6) Health and fat

6-1) Trans fatty acid


There are two different types of molecules among unsaturated fatty acids containing double bonds. It is named Sys · Trance. Cis is in the form of a molecule bent with double bonds, with a carbon skeleton on the same side of the double bond. This is the form of the molecule contained in the natural vegetable oil. Because of this bending it is difficult for molecules to gather, it does not become a solid, it becomes a liquid oil.


Margarine · shortening adds hydrogen to harden liquid vegetable oil. At that time, a transformer type will be formed in the double bond.


Trans fatty acids are unsaturated fatty acids but differ from the double bonds of natural plants. The risk of cerebral infarction is suspected and intake should be modest.


We also try to eat well-balanced polyunsaturated fatty acids with good balance.

When the ice melts out, a second phase other than water and ice appears. Bismuth,too.

When the ice melts out, a second phase other than water and ice appears.

I believe similar phenomena are occurring in ceramic firing.

When the ceramic is baking,
Do not raise the temperature until it becomes liquid.

Although it is solid, there are some components close to the melting point.

It turns into a liquid and becomes solid again as it becomes frozen.

When the liquid component becomes solid
Oxidation becomes insufficient,
It is the idea to disturb the insulation properties.

In order not to make this liquid component,
Firing at low temperature,
It is firing at high temperature to oxidize the resulting liquid component.

This is because
When sintering at 700 degrees, leakage current of SrBi2Ta2O9 (SBT) film is small,
Even though it is even 800 degrees,
The fact that if the firing is done at 750 degrees, the leakage current of SBT  increases.
It can be explained.

For the crystallization of bismuth layered ferroelectric SrBi 2Ta2O9,

Oxygen partial pressure is related greatly.

With less oxygen, even at 700 degrees or less
To crystallize.

However, as leakage characteristics at this time
There is not enough consideration.

Bake the SBT thin film made at 700 degrees again at 800 degrees,
Electrochemically Etching out fine components,
in a gas or liquid that promotes oxidation of trace components Reoxidize.
Ultrasonic cleaning in nitric acid or sulfuric acid.
It may unexpectedly let the fine component rinse out.

The SBT film made by baking at 800 degrees,
It has no leaks and it has hydrogen resistance.

This will be the original strength originally possessed by the SBT crystal.

Looking at it as a films, I can not use it,
Due to the fine components of the substrate interface and particle interface,
Almost, as expected.

It is important that the fine components as bismuth poor pyroclore crystals must be made or be replaced.
Because that fine bismuth poor crystals can reduce the SBT insulator crystal  around those to topological insulator. 

New Idea; Bismuth Ferroelectric thin films as Topological insulator crystal

Topological insulator.
It is an insulator crystal thin film in which only the surface of the crystal flows electricity.
1) The crystal is not uniform. There may be a state where the insulator crystal is surrounded by the reducing crystal.
2) Reducing crystals oxidize themselves by reducing counterparts. It gives electrons and robs oxygen.
3) BLSF is a topological insulator and bismuth-deficient pyrochlore crystal is in a reducing crystal relationship.
4) Only low-reducing fluorite crystals are formed at low temperatures depending on the firing temperature. Even in high-temperature firing, it becomes a BLSF homogeneous phase.
5) In the case of firing at intermediate temperature, reducing pyrochlore is generated and the topological insulator is exposed.
6) In the BLSF, when the crystal surface is reduced, the crystal surface becomes electrically conductive.
7) As the reduction of BLSF progresses, metal bismuth precipitates at the triple point.

If such consideration could be made 20 years ago, it became a master's thesis that I could understand a little more.


The greater the difference in ionization tendency is, the stronger the reducing property is.

The strontium / tantalum oxide having less bismuth is easily oxidized, and the reducing property is strong.

If added to SrBi 2 Ta 2 O 9,
 Li (s), E ° = -3.045 V
Ba (s), E ° = -2.92 V
Sr (s), E ° = -2.89 V
Al (s), E ° = -1.676 V
Ti, E ° = -1.63 V [3]
Mn (s), E ° = -1.18 V
Ta (s) + 5 H 2 O, E ° = - 0.81 V
Fe (s), E ° = - 0.44 V
Pb (s), E ° = - 0.1263 V
H 2 (g), E ° = 0 V
Sb (s) + 3 H 2 O, E ° = 0.1504 V
Bi (s), E ° = 0.3172 V
Cu (s), E ° = 0.340 V


SBT is expected to be E __ = -0.4 to -0.6 V.
Although E ゜ = 0 V hydrogen is not reduced,
E ° = - 0.9 V Strontium · Tantalum oxide reduces the surface to bismuth metal.

In the mechanism, hydrogen becomes a hydrogen ion with a platinum electrode.
Hydrogen ions first reduce strontium tantalum oxide.
Reduce the BLSF crystal that is in contact with the oxygen-deficient form of the resulting strontium-tantalum oxide.
The surface reduced from BLSF shows electrical conductivity.

Policy 1) Do not make reducible pyrochlore.

Policy 2) Decrease reducibility of reducible pyrochlore

Policy 3) Add a component that will become an insulator even if reduced to SBT.


In other words, pyrochlore promotes reduction of BLSF by providing a step to BLSF which is not easily reduced.

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Development of Bismuth Layer Perovskite Ferroelectric Thin Films for Non-Volatile Memory (1998)

Ferroelectric thin-film capacitors have been extensively investigated with high expectations for nonvolatile memory application. The memory is substituted SiO2 in DRAM to Ferroelectric material as shown in Fig.1. Fig.2 shows the material have shows polarization hysterisis, which character used in memory judgement 1 / 0. Pb(Zr,Ti)O3 is one of the most Popular materials. However, Pb(Zr,Ti)O3 thin films tend to degrade most of the initial amount of switching charge after 10^8 cycles of full polarization switching(so-called fatigue).



Recenty, it has been found that ferroelectric Bi layered structure oxides such as Sr Bi2 Ta2 O9 has excellent high fatigue resistance. Their crystal lattices are orthorhombic and consist of two connected layers of TaO6 octahedra, which are perovskite layers,separated by Bi2O2 layers as shown in Fig.3. Fig. 4 shows material shows fatigue character of Sr Bi2 Ta2 O9 thin film which keep remanent polarization (Pr) after 10^12 cycles. We are studying various Bi layer structured compounds using an improved sol-gel method.

1. Introduction

In recent years, aimed material development for ferroelectric nonvolatile memories has been actively developed in each research institution, and among them, SrBi 2 Ta 2 O 9 (SBT) oxide ferroelectric thin film is attracted much attention because fatigue phenomenon against polarization reversal hardly occurs. Many examples of this SBT thin film are produced by a coating thermal decomposition method using a carboxylic acid salt in many cases. For this heat treatment, relatively high temperature heat treatment has been required in the silicon process of 800 ° C. Therefore, we have developed total alkoxide type solution and investigated low temperature formation of SBT thin film.

Furthermore, the relationship between the electric characteristics and the firing temperature was examined. Bismuth layered ferroelectric crystal (BLSF) particles were formed with increasing temperature of 700 ° C and 750 ° C, and the amount of polarization increased. It has already been reported that ferroelectric BLSF particles are formed on the whole surface of a thin film calcined at 800 degrees, indicating sufficient polarization. Therefore, in order to prepare a ferroelectric thin film, a crystallization process changing from a fluorite structure to a layered structure is important. In particular, focusing on the change in the firing temperature of the microcrystalline region which has not changed to BLSF, in spite of the start of formation of BLSF at 700 ° C., in order to obtain a BLSF single phase film. It was aimed to clarify the reason why firing is necessary.

2. Experimental method

After applying the whole alkoxide type solution, preliminary firing was carried out, and the thin film which was actually sintered at 650, 700, 750 degrees was examined. As the alkoxide, one having 4 or less carbon atoms was used. Sr (OC 2 H 4 OC 2 H 5) 2 was used as the Sr source. Bi (O - nC 4 H 9) 3 and Ta (OC 2 H 5) 5 were used for Bi source and Ta source for each liquid. The charging ratio was Sr 0.7 Bi 2.3 Ta 2 O 9. For the substrate, Pt (60 nm) / SiO 2 (100 nm) / Si (6-inch wafer) formed by a sputtering method was used. Coating was performed with a spin coater. The coated film was dried at 150 ° C. for 30 minutes and then pre-baked at 450 ° C. The above process was repeated 8 times to obtain a thin film with a thickness of 0.2 μm. After repeating the above steps, the main firing was carried out in an oxygen atmosphere for 1 hour. The firing temperature was 800, 750, 700, 650 ° C. Electrical characteristics were evaluated using Radiant RT66A after forming the upper Pt electrode by sputtering. For the crystal structure analysis, a transmission electron microscope (TEM; H-8100, Hitachi, 200 kV) was used. For composition analysis, energy dispersive X-ray microanalyzer (EDX) attached to TEM was used.


3. Results and Discussion

First, we studied compositional change of microcrystal part present in thin film calcined at 650 ℃ to 750 ℃ ​​due to rise of firing temperature. Composition analysis revealed that the bismuth concentration in the microcrystalline region decreases at 700 and 750 ° C compared to the layered structure crystal. And the decrease in the amount of bismuth in the microcrystalline region becomes significant due to the rise in the firing temperature.
Regarding the change in the microcrystalline part, crystal structure analysis was carried out by electron beam diffraction of the crystal region. The figure shows the limited field diffraction pattern from the microcrystalline region of the thin film fired at 650, 700, 750 ° C. It can be confirmed that the ring at 650 ° C. shows the 111, 200, 220, 311 faces of the fluorite structure. Next, at 700 ° C., the diffraction pattern likewise shows a fluorite structure, and no remarkable change is observed in the crystal structure. Here, in the thin film fired at 750 degrees, a diffraction pattern from the surface of about 6.2 A appears newly inside the fluorite structure diffraction ring. Therefore, a new phase formed at 750 ° C could be identified as a pyrochlore phase. In other words, it was confirmed that the bismuth composition decreased in the microcrystalline region and the crystal structure was changed from the fluorite to the pyrochlore structure.


4. Summary

In the crystallization of SBT, in the calcined film of 750 degrees, the microcrystalline part changes from a fluorite structure to a part to a BLSF crystal, and the rest changes to a pyrochlore structure. Because this pyrochlore is difficult to change to BLSF, it can be considered that it could not be a BLSF single phase film at 750 ° C firing. This structural change is thought to be due to the formation of a low bismuth region by the diffusion of bismuth and the structure change. Therefore, in order to suppress the phase transition which changes from the fluorite structure to the pyrochlore structure, it is necessary to suppress the migration of bismuth.





Study on SBT thin film with reduction resistance focusing Behavior of metal bismuth

[Introduction]
 In order to achieve high integration of ferroelectric memories, it is necessary to enhance the process resistance of ferroelectric thin films, particularly chemical stability. Particularly, in the passivation process during the silicon process, the heat treatment atmosphere in the reducing atmosphere is exposed, so degradation such as leakage of the ferroelectric or lowering of the residual polarization has been regarded as a problem. Research on improving hydrogen tolerance by PZT thin film by improving electrode has been reported, but the resistance to Pt electrode is low. Furthermore, it has been reported that SBT with excellent switching characteristics has lower hydrogen resistance than PZT. We have reported that reduction of leakage current and RTA compatibility can be improved by using proprietary sol / gel type alkoxide solution as SBT thin film forming solution. We believe that these process resistance improvements are due to the fact that the Bi - rich component at the grain boundary of the SBT crystal could prevent precipitation. For the SBT thin film which improved the reduction resistance by improving the solution, chemical state analysis was carried out, and quantitative analysis of the oxidation state of bismuth was carried out in particular.

【Experiment】 Alkoxide mixed solution (composition Sr 0.7 Bi 2.3 Ta 2 O 9) solution and sol -gel solution (composition Sr 0.9 Bi 2. 1 Ta 2 O 9) was used. SBT thin films were formed on Pt / SiO 2 / Si substrates, respectively, and subjected to furnace processing (FA) at 800 ° C. and rapid heating (RTA). The surface chemical state was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS).

【Result】

For the sample used in this analysis, comparison was made between a mixed alkoxide sample which can not be measured for ferroelectricity and a sol-gel sample which can be measured after hydrogen sintering (400 ° C., 15 minutes) as a reduction resistance test.

1, Influence of composition ratio

The figure shows the respective hysteresis loops of mixed alkoxide type and sol-gel method SBT. In the sol-gel film, it is a low bismuth composition film in which the excess amount of bismuth charged is reduced, but it is not different from the bismuth excess added film so far and shows a sufficient Pr value. The film quality when the composition ratio is changed from Sr 0.7 Bi 2 .3 Ta 2 O 9 to Sr 0.9 Bi 2. 1 Ta 2 O 9 is compared. The figure is a surface SEM image of each of mixed alkoxide type and sol-gel method SBT. In the mixed alkoxide system, stone wall-like particles are formed on the entire surface and a BLSF single phase film is formed, but the particles are formed like stone walls.
 On the other hand, even with the sol-gel method, although the fine particle part remains slightly, the BLSF particles are formed on almost the entire surface, and therefore, it is considered that a sufficient Pr value is shown.

The stoichiometric value of the SBT crystal is SrBi 2 Ta 2 O 9, but at present other research institutes are currently formed with a composition of Sr 0.7 Bi 2 .3 Ta 2 O 9 by using a carboxylate. At this time, it is reported that there is an effect of replacing the bismuth excess with Sr and increasing the residual polarization Pr. Or it is supplemented as a burned-out portion. However, in our system, burn-out of bismuth composition is not observed even at 800 ℃ calcined film.
No significant increase in Pr due to substitution with strontium has been observed. Therefore, we considered that the role of excessive bismuth is important to help the phase transition from fluorite crystals to BLSF crystals.

Studies on the phase transition from the previous fluolite to BLSF report that the change to BLSF is inhibited as it is thermally stable once the pyrochlore phase is formed. Since this pyrochlore bismuth deficient composition tends to be formed when locally generated, it is easy to form a pyrochlore by reducing the excess amount of bismuth in the charged amount, making it difficult to obtain a single phase film of BLSF is expected. In this study, we also succeeded in promoting the formation of BLSF with this low bismuth composition by using the sol-gel method for the purpose of increasing the sinterability to the state close to the BLSF single phase even in the low bismuth composition film .



2. Metal bismuth

We have reported that the peak of metallic bismuth is observed from chemical state analysis of mixed alkoxide film. The figure further shows the XPS chart before and after slight dry etching of the surface by argon etching. It is found that the metal bismuth is abruptly increased by Ar etching. At this time, it is considered that there is a possibility that particles whose bismuth covers the outside of the metallic bismuth may be present as the reason why only bismuth is easily reduced.

The figure is an XPS chart of the mixed alkoxide film fired at 650 ° C. The bismuth metal exists in the fluorite fine particle film fired at 650 ° C, and the tendency for bismuth to be readily reduced by Ar etching is remarkable.

We point out the existence of particles that are excited by electron beams such as fine particles in these microcrystals or voids inside the BLSF and vibrate. This easily oscillating particle is considered to be metal bismuth particles reduced by Ar sputtering.

This bismuth metal behaves as a function of bismuth excess particles precipitated in grain boundaries and microcrystalline regions.



XPS analysis of the SBT thin film surface with the mixed alkoxide solution showed a peak of the metal state of Bi, in particular. Furthermore, it is confirmed that bismuth-rich fine particles are precipitated at the grain boundary. That is, as a feature of a sample having a low reduction resistance, the presence of a grain boundary instability component and the result of a quantitative analysis of Bi (metal) detected in a thin film formed by using two kinds of forming solutions are shown in the figure . In the mixed solution of alkoxide, the proportion (Bi-metal / (metal + oxide)) of metallic bismuth in the total bismuth amount of both FA and RTA shows a high value of 3% or more. On the other hand, the amount of metallic bismuth is kept extremely low in both the FA and RTA treatments in the SBT film made of the sol-gel solution having reduction resistance. This is consistent with the decrease in the amount of precipitated Bi particles at the grain boundaries observed by EDX. From the above, it can be judged that stabilization of the SBT grain boundary is made by sol-gel solution. At this time, metal bismuth is suppressed by the film having reduction resistance, and it can be judged that the amount of metal bismuth has a large influence on reduction resistance.

Based on the studies so far, the reduction site easily precipitates bismuth-rich particles segregated at the grain boundary or the metal state bismuth fine particles are present, and if a certain amount or more of leakage current exists, the dielectric strength is We believe that there is a critical amount that causes extreme drops.

In order to reduce bismuth in this metal, the merit of sol-gel method which can mix even oxygen atom and metal atom atomic level from solution is utilized.

The semi-metal bismuth itself has a topological character !!

The semimetal bismuth itself has a topological character.

http://news.mynavi.jp/news/2016/11/22/263/

The topological was not because by a special complex crystal structure , but by the nature of crystals centered on bismuth.

The University of Tokyo Graduate School of Science PhD course Doctoral course Mr. Shun Ito,
Associate professor Iwawaru Matsuda Institute for Physical Properties, The University of Tokyo,
Ochanomizu University Faculty Research Institute Professor Koji Kobayashi
These are the achievements.

By reading the article, by observing the band structure by photoelectron spectroscopy,  they measure the topological nature.


The bismuth thin film may be used at that time.
There was no condition to prepare the bismuth thin film in the short article.
Regardless of the film forming method, it is possible to produce a crystal thin film of a similar polycrystalline type.
Depending on the film formation conditions and the firing temperature, such a polycrystalline type thin film was known that insulation property changes.

Why it is important for insulation to change ?
It was because we tried to use bismuth based insulating thin film as a capacitor of memory.
Naturally, insulation is a key factor in performance.

Bismuth-containing ferroelectrics are not only insulative but also have the property of retaining dielectricity even when normal voltage is applied.

I was studying that Bismuth films 20 years ago.

Since SBT (SrBi2Ta2O9) is a typical bismuth ferroelectric, that can be much potential  to make memory device.
But SBT films can not be memory device because of its leakage current.

Thinking now,
There is probably a topological nature and leak current will flow.

In fact, the firing temperature and the topological leakage current are related.

We observed the existence of pyrochlore fine crystals was created by baking at low temperature.
At those  days, I thought that pyrochlore fine crystals in the films may flow current.
Now, I think that pyrochlore fine crystals reducing around the insulating crystal to semi-metal bismuth.
That semi-metal bismuth is exist. We observed by XPS measurement that the peak shift of Bismuth. 

In near future, the bismuth contained in pyrochlore fine crystals will close up.

The condition of bismuth in Pyrochlore and the insulated crystal around  those fine crystals is very depend on baking temperature and the topological factor is also depend on temperature.

The mechanism the Pyrochlore crystal reduce the around insulator crystals is related to red-ox  tendency of those elements, I think.

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名古屋の人気ブログ 愛知ハッピーをよろしく。今日も更新中。 https://t.co/mpEtx7j83E

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NY株、大幅続落で取引開始 https://t.co/r4KbLa1y7z #スマートニュース

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名古屋の人気ブログ 愛知ハッピーをよろしく。今日も更新中。 https://t.co/mpEtx7j83E

名古屋の人気ブログ　愛知ハッピーをよろしく。今日も更新中。　https://t.co/mpEtx7j83E

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どんどん庵が、もともと安いうどんを 期間限定でさらに激安に。 安すぎてついでに天婦羅を食べてしまうのでトータルでは、それほど安くならない。 さらに割引券をくれた。 汁は名古屋の赤いヤツが美味しい。

どんどん庵が、もともと安いうどんを

期間限定でさらに激安に。

安すぎてついでに天婦羅を食べてしまうのでトータルでは、それほど安くならない。

さらに割引券をくれた。

汁は名古屋の赤いヤツが美味しい。

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右脚の腿が一昨日から痛い。 エアーバイクの漕ぎ過ぎなのか? 左は何ともない。 湿布を貼るぐらいしか対処は思いつかない。 湯船でゆっくり温めると楽になる。 寒すぎ。

右脚の腿が一昨日から痛い。

エアーバイクの漕ぎ過ぎなのか?

左は何ともない。

湿布を貼るぐらいしか対処は思いつかない。

湯船でゆっくり温めると楽になる。

寒すぎ。

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The homemade soap Chemistry on the environment and health

Learning with homemade soap Chemistry course that is really friendly to the environment and health


Early 2015 Nagoya Environmental University Co-education lecture Kiyoyuku (May, Heisei 20)


Learning here is about not only about soap but also basic knowledge of chemistry for greases and environments that are widely useful for health.

1) Science and the environment

There is only one earth, plants, animals, and humans live. Activity is also indispensable for human life by obtaining food with agriculture. The farming is also done on a worldwide basis, not a local pond disappearing like the old, but many foods are imported from abroad. Also, when you consume them you get garbage. For such human life, grease and soap to wash it are essential items.

1-1) Food self-sufficiency rate

While there are food exporting countries whose main countries' food self-sufficiency ratio exceeds 100%, Japan has fallen to a very low self-sufficiency rate of around 39%. It is also manifesting as a figure of reality self-sufficiency that fields and rural landscapes have disappeared from personal belongings. A decline in the self-sufficiency rate means that imports of food from overseas are increasing.

1-2) Food mileage

Here I will explain the concept of food mileage. Food mileage is the number of food consumed (weight) × distance traveled (Km). It is an indicator of how far from the local production pond disappears how far you are eating the food you have brought from far. Looking at the figure below, Japan knows that food mileage is also very big in the world. There are also many population living in a narrow country. Food mileage is also big in South Korea where the country is narrow, but it is not as much as Japan. France, which is an agricultural country, has a small value. The country is small UK, Germany, which is an industrialized country, also has a smaller food mileage than Japan.

In case

2) Chemistry of soap

Now that I have found the outline of Japanese food situation, the next is about fat and oil of soap material. Soap materials are oil and caustic soda and water. In addition to natural fats and oils, oils and fats can also be used as fatty acids derived from petroleum. Caustic soda is a strong alkaline chemical among the "acid / alkali" categories. Sodium bicarbonate is representative in alkali in daily life. Sodium bicarbonate and caustic soda contain the same mineral as sodium.

2-1) Carbon

Mixing grease, caustic soda and water produces a byproduct of soap and glycerin. Carbon C (carbon) is indispensable when considering the chemical formula of oils and fats. As you can see from the fact that charcoal (soot) can be produced by burning fats and oils, it is made up of gatherings of carbon and others. Carbon occupies most of the body of plants that have taken up carbon dioxide in the air. Let's remember carbon is the material of plants and animals.

2-2) Caustic soda

Well, another material of soap was caustic soda. Caustic is a word meaning that the skin becomes rough, and soda is sodium. Sodium is a mineral component of salt. It is an essential mineral contained in seawater and the body. It has properties which are easily soluble in water. The reaction of mixing hydrochloric acid and caustic soda is a reaction of acid alkali. I can make salt and water. It is strange a little.

2-3) Oil and fat

Fats and oils refer to the oil in general, which is used everyday, including liquid oil and fat solidified at room temperature. Materials such as soybean oil, palm oil, rapeseed oil, etc. are produced in large quantities. Especially olive oil and Laurel oil etc are used in Europe for a long time and are also famous as a material for soap. Petroleum and coal are said to have originated from the carcass of plants and animal carcasses in the soil. Petroleum coal refining oil and rapeseed oil oil have the same chemical structure. Nevertheless, rapeseed is much better than oil that can be regenerated in the sunlight in a year, petroleum coal has been in the past several hundred million years

There is also a difference that it uses the oil of animals and plants that have been exposed to sunlight for many years such as momentarily. Any oil will mix unpurified impurities. It is called impurities or trace ingredients. Anxiety remains in such impurities in petroleum and coal derived oils. On the other hand, it is said that some trace components of renewable vegetable oil such as olive oil can be expected to have a good scent and a good effect on the skin, which is heavily used.

In case

2-4) Plantation

Palm oil and the like are oils like representatives of renewable energy which can be harvested 12 times a year in vegetable oils and has high production volume. However, it opened up a rainforest in Southeast Asia such as Malaysia and Indonesia and created a huge plantation that cultivates only a single variety called plantation. Global warming has been accelerated by the plantation. Local life farmers' lives have not necessarily become wealthy. There are aspects that press the circumstances of European and American developed countries to Southeast Asia and others.

3) Health and the environment

3-1) Oils and fats and health

Well, if we look at this oil in relation to health, it is the balance of the three major nutrients, P protein, F fat, C sugar. Dietary habits such as America and France take too much fat and in Vietnam and Thailand it seems like taking too much sugar. I think that it can be said that the balance of protein, fat, and saccharide is superior in Japan's dietary life.

3-2) Soap and environment

Talk to soap and think about the relationship with the environment. Soap removes grease so it is essential to life. The soap-containing water flows back into the river and then returns to the original water after biodegradation by microorganisms. Microorganisms eat soap and break down. Synthesis in soap

Soap LAS is what used to be. With synthetic soap, the shape of the molecule did not branch and it was linear soap. It turns out that in the graph, it takes time to be biodegraded. This was also improved by making branched synthetic soap.

Also, the soap of natural ingredients is easy to biodegrade and looks good to the environment. This is also a numeric magic, it is certain that soap is easily decomposed when the same amount is melted, but soap is difficult to foam, it will be used a lot. In other words, it is often used in a lot of dissolved in water.

3-3) Soap and environment

Molecular structure of soap generally has a molecular structure in which a part soluble in water and a part soluble in oil adhere to each other as shown in the figure. There is sodium in the water-soluble part. Oil and friends are originally derived from oil and have a structure of about 12 to 20 carbons in a row. Longer carbons are good friends with oils, and if they are short, they become more soluble in water. The detergency of soap is built on these balances.

For soap and detergents, it is most important to reduce the amount used as much as possible.

3-4) Soap and water

In order to reduce the amount of soap used, the point to think is on the side of the water. There are water that is easy to foam using soap or water that is not foamable. They are trace minerals in water, that is, the amount of magnesium and calcium in the water varies from country to country. It is called hardness of water.

The figure shows mineral water arranged in order of soft water to hard water. The water in Japan is soft water. Water in Europe, especially the Alps, is hard water.

3-5) Hard water

Soap is easy to dissolve in water, so foams have detergency. However, magnesium and

When calcium is high, soap and soap combine to form soap scum and metal soap that do not foam. These will reduce the feeling of use of soap. Also foaming falls, so the amount used will increase. It is a chelating agent that prevents it. A chelating agent called EDTA (edetic acid) is the representative. Chelate means scissors in the crab and it works to catch magnesium and calcium inside the chelating agent as shown in the figure. Thanks to that, soap lather is greatly improved. I think that it is good to limit the use to very small amounts.

3-6) Hard water in Europe

In the hard water of Europe, it is often that the same soap as in Japan has poor foaming and can not be used. In Japan, solid soap containing sodium is common, but liquid soap containing potassium instead of sodium is common in Europe. Potassium liquid soap is used in washing places of public toilets, etc. in a melon-like round container etc even in Japan. If that liquid soap, you can remove dirt with hard water.

4) Summary

To summarize so far the story of the soap and the environment, soap is not good for river environment either synthetic or natural. It is important to wash with a small amount of soap. And I think that it is important to consider the environment of the production process.

4-1) Environmentally-friendly fats and oils

Given the conditions of good oil for use in soap, you will find that there are conditions such as being mass cheaply available, being gentle to the skin, easy to biodegrade. What is oil and grease good for the environment and health? It seems that the production amount of animal and vegetable oils and fats in the present world is less than 80 million tons. Soybeans and palm account for 50% of them. They are mainly used for food. It is also used for industrial use.

Titanium oxide can decompose water with ultraviolet rays "Honda Fujishima effect"& Topological insulator

It is known that titanium oxide can decompose water with ultraviolet rays.
This is the source of discovery of Honda Fujishima effect.

Titanium oxide is used as a photocatalyst by decomposing organic matter to keep the coated surface clean.

Why can titanium oxide decompose organic matter at this time? What?

This is also considered from the ionization tendency and redox potential.

The following is a quote from my blog.

The greater the difference in ionization tendency is, the stronger the reducing property is.


The strontium / tantalum oxide having less bismuth is easily oxidized, and the reducing property is strong.

If added to SrBi 2 Ta 2 O 9,
 Li (s), E ° = -3.045 V
Ba (s), E ° = -2.92 V
Sr (s), E ° = -2.89 V
Al (s), E ° = -1.676 V
Ti, E ° = -1.63 V [3]
Zr, E ° = -1.534 V [3]
Mn (s), E ° = -1.18 V
 Ta (s) + 5 H 2 O, E ° = - 0.81 V
Fe (s), E ° = - 0.44 V
Pb (s), E ° = - 0.1263 V
H 2 (g), E ° = 0 V
Sb (s) + 3 H 2 O, E ° = 0.1504 V
Bi (s), E ° = 0.3172 V
Cu (s), E ° = 0.340 V


SBTO is expected to be E __ = -0.4 to -0.6 V.
Although E ゜ = 0 V hydrogen is not reduced,
E ° = - 0.9 V Strontium · Tantalum oxide reduces the surface to bismuth metal.

In the mechanism, hydrogen becomes a hydrogen ion with a platinum electrode.
Hydrogen ions first reduce strontium tantalum oxide.
Reduce the BLSF crystal that is in contact with the oxygen-deficient form of the resulting strontium-tantalum oxide.
The surface reduced from BLSF shows electrical conductivity.



The oxidation-reduction potential of titanium can be estimated to be -1.63 V.
Beyond this potential, titanium is reduced by light,
The property of reducing opponent and trying to return to titanium oxide,
I think that it is the essence of reducing and decomposing organic matter.

Apart from titanium, near potentials are zirconium, manganese, tantalum.
For these to work as a photocatalyst,
First, it is decomposed by light,
Does it have the property of returning itself to oxides by reducing around them shortly afterwards? That is the deciding factor.

When quoted,
””””
Visible light responsive photocatalyst, method for producing the same, and method of using same


PROBLEM TO BE SOLVED To develop a visible light responsive photocatalyst having sensitivity to any visible light region such as an incandescent lamp, white LED, sun natural light and the like and having activity for photolysis of water.
SOLUTION: This photocatalyst mainly composed of zirconium oxide and graphite or graphite silica exhibits water decomposition performance of quantum yield of 30% or more even in a visible light region containing almost no ultraviolet light of 60 to 100 W incandescent lamp photocatalyst.
DETAILED DESCRIPTION OF THE INVENTION
【Technical field】
[0001]
TECHNICAL FIELD The present invention relates to a visible light responsive photocatalyst, a method of manufacturing the same, and a method of using the same.
BACKGROUND ART
[0002]
As a photocatalyst having visible light activity, titanium oxide-based ones are dominant (for example, JP-A Nos. 2003-260370, 2004-330074, 11-333302, and 11-333304).
[0003]
On the other hand, zirconium oxide is said to have a large hand cap and can not respond to visible light, but also with respect to those using this, as described in JP-A-2009-106897, JP-A-2003-117407, JP-A-2007-75678 And so on.
[0004]
Of these, JP-A-2009-106897 discloses a visible light responsive photocatalyst in which tungsten oxide particles of 0.05 μm or less are adhered to the surface of a white pigment such as titanium oxide or zirconium oxide with respect to zirconium oxide.
[0005]
In addition, JP 2007-75678 discloses a visible light sensitive functional oxide containing niobium, tantalum, or antimony, Cr, Fe or the like in zirconium oxide.
””””


As described above, besides titanium, zirconium, manganese, and tantalum can also be photocatalysts at close potential.

These metals show the effect of decomposing organic substances with reducing power.


I'm watching these are also involved in redox at the crystal grain interface.
When the reduction of the crystal grain interface occurs,
The topological insulator of the Nobel Prize in Physics is formed.

By irradiating ultraviolet rays on the material combined with bismuth and photocatalyst,
Microscopic reduction occurs,
I believe that the surface of the insulating crystal is reduced to show conductivity, which is also the expression mechanism of the topological insulator.

BLSF bismuth layered ferroelectric crystals as a topological insulator

We take up one of BLSF bismuth layered ferroelectric crystals called SrBi2Ta2O9 (SBT) as a topological insulator.
From the firing temperature, crystal structure and fine composition analysis of SrBi 2Ta2O9 (SBT) crystal, the mechanism of expression of topological insulator is discussed based on red-ox potential.


Since SBT has less membrane fatigue due to polarization reversal and can extend the life of ferroelectric memory.
It was studied in 1996. However, leakage current flowed during hydrogen gas treatment and insulation characteristics decreased, making it a material hard to use as a memory, and practical application was limited.

Considering why hydrogen gas reduces insulation,
It is easy to explain using the topological idea of ​​the 2016 Nobel Prize in Physics.
Here, "topological" refers to a physical phenomenon in which only the surface of the crystal grain is altered in the film which is a cluster of crystal grains.

The interior of the SBT crystal is not reduced with hydrogen gas, and it is almost in its original form.
Assuming that the oxidation-reduction potential of hydrogen gas is 0 V,
Base metal lithium is 3V
Strontium is 2.8 V
Titanium is -1.6V
Tantalum is - 0.8 V
Lead is 0.1V
Bismuth + 0.3V
Copper close to precious metal is +0.34 V

And the oxidation-reduction potential in an aqueous solution.
The electrode uses precious metal platinum.

Precious metals are prone to metal
Base metals tend to become oxides and are reduced and hard to become metal.

Probably SBT is an oxide that is more base than lead + 0.1V lead than bismuth + 0.3V.


In estimation, since it has an oxidation-reduction potential of about -0.8 V
The inside of the crystal is not reduced with hydrogen gas.

In Real, the main SBT crystal is not destroyed by hydrogen gas heating. 

However, from firing temperature and crystal structure analysis
Microcrystals structure(low temperature phase) of the Bismuth oxide Films  are not reduced much.

Large crystals (high temperature phase) of the SBT structure are not reduced to the inside.

Among the intermediate phase pyrochlore microcrystals,
Resistance-reducing pyrochlore (low-temperature type) is similar to fluolite and has characteristics that it is not reduced much.

It can be analyzed that its composition ratio is 0.7: 2.3: 2 to 0.9: 2.1: 2 for S: B: T.
The easily reducible pyrochlore (high temperature type) is prone to be specifically reduced, and further has the property of oxidizing itself and reducing the contacted crystal.
It can be analyzed that S: B: T is about 0.7: 1.5: 2.

In particular, the defect of bismuth is characteristic, and the defects of strontium and tantalum are not clear.

This is presumed that bismuth is caused by movement to the inside and outside of the membrane called migration at a particularly low melting point.

When this easily reducible pyrochlore (high temperature type) appears,
This is easy to reduce.

However, it is reduced unilaterally and not a metal.
There is an event that can be explained by assuming a mechanism that pyrochlore is oxidized again and reduces the SBT crystal in contact with it.

It is SBT crystal film fired at 750 ℃.

Although SBT crystals occupy about 80%, it has been confirmed that about 20% high temperature type pyrochlore exhibits a crystal structure distributed in gaps.

The leakage characteristic at that time has a very large current value,
It also has low fatigue resistance.

Although SBT has a similar crystal,
The characteristics do not show the inherent insulation and fatigue resistance of the SBT.

Even with films with low temperature pyrochlore, insulation is overwhelmingly low and fatigue properties are poor.

To illustrate this,
It is presumed that the crystal surface of SBT is topologically conductive.

We also believe that its topological conductivity is responsible for metallic precipitates such as bismuth and alteration of SBT surface.

The mechanism by which the surface alteration of SBT occurs.
It is inferred that the aforementioned high-temperature type pyrochlore is a bismuth deficient type, that is, a base oxide rich in tantalum strontium, and because of the nature of tantalum, it is easy to reoxidize, that is, the surface of the contacted SBT crystal is easily reduced .

In other words, the easily reducible pyrochlore has an oxidation-reduction potential of between -0.9 and -2.8 V.


There is bismuth of + 0.3 V partly,
The difference is expected to be large.

That is, a part to be easily reduced and a part which is oxidized from reduction to reduce partner appear.


From the above,
1) SBT leakage current is caused by SBT crystal surface topological conductivity.

2) The surface topological conductivity of the SBT is caused by the mechanism caused by the force of reducing the surroundings once the bismuth defective pyrochlore around it is once reduced.

Guess the model
Therefore, it can be concluded that making a bismuth deficient pyrochlore will help reduce leakage current.

In addition, it is thought that it is necessary to make the composition ratio and constituent elements that do not become easily reducible pyrochlore.


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In perovskite solar cells, thermal degradation is an obstacle to commercialization

In perovskite solar cells, thermal degradation is an obstacle to commercialization. The mechanism of structural change and chemical change caused by heat was revealed by in situ measurement of transmission electron microscope.

Article: In situ Observation of Thermal Degradation of Perovskite Solar Cell

In situ observation of heat-induced degradation of perovskite solar cells
doi: 10.1038 / nenergy.2015.12

Altmetric: 2 Views: 859 Citations: 1 More detail
Article

In situ observation of heat-induced degradation of perovskite solar cells
G. Divitini, S. Cacovich, F. Matteocci, L. Cinà, A. Di Carlo & C. Ducati
Nature Energy 1, Article number: 15012 (2016)
doi: 10.1038 / nenergy.2015.12
Download Citation
Characterization and analytical techniques | Solar cells | Solar energy and photovoltaic technology
Received:
25 August 2015
Accepted:
18 November 2015
Published online:
18 January 2016

http://www.nature.com/articles/nenergy201512?WT.mc_id=SFB_Nenergy-201602_JAPAN_PORTFOLIO
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Research on perovskite solar cells has been actively conducted in recent years.
Its energy conversion efficiency (PCE) exceeds 15%. Furthermore, the device can be made by solution coating and it has the advantage that it can be manufactured at low cost.
The important role of this solar cell is organic-inorganic hybrid type perovskite compound (MeNH 3 PbI 3) of semiconductor material used as light absorption layer.
By using high purity lead iodide (II) as a raw material for perovskite compound, it becomes possible to create excellent solar cell devices.
""""

When I read the abstract of the paper mentioned above,I was surprised.

On observation the Perovskite thin film With a transmission electron microscope, with heating  it in situ, the movement of chemical components and the resulting physical structural change by heat was cleared.

It is said that it was found to be the cause of deterioration.

In particular, as a chemical component,
Migration of lead and iodine is a problem.
Since lead has a low melting point and is easy to volatilize, it is natural that components will move or volatilize if heated.

I was slightly surprised that iodine has properties similar to that.

Why investigate thermal stability in the first place?

Because The thin film of PbI perovskite type will be useful  for solar cell.
But it's Heat stability improvement must be  desired.

The PbI perovskite was a crystal that hardens almost without heating, it actually require heating in the formation process.

By rising heat while receiving commercial sunlight, they may degrade.

Even though instantaneous efficiency is good,The future is low.

I say, now
Similarly for bismuth-based ferroelectrics thin films, migration of bismuth occurs,
It is reported that the structure formed by this is different and the performance changes.(JJAP 1998)

This time, the migration of lead and iodine is also heated,
It is expected that migration in the membrane and volatilization into the air occur.

Particularly, lead is volatilized in the air is not good for the environment and it is not good in terms of performance.

For Developing lead-free perovskite type solar cells,
If thermal stability is not realized,
Practicality as a solar cell is low.

Heat stability improvement is desired.

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次の仕事の面接をいくつも受けている。

どこの会社の面接でも
好感触
受かる
採用決定
と思わせて、
一社も内定がない。

— 木陽塾（榊原あざみ） (@mokuyojuku) February 6, 2018

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February 06, 2018 at 07:13PM
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