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.