This title appears in the Scientific Report :
2023
Please use the identifier:
http://dx.doi.org/10.3390/cryst13081278 in citations.
Please use the identifier: http://dx.doi.org/10.34734/FZJ-2023-03389 in citations.
An Operando Study of the Thermal Reduction of BaTiO3 Crystals: The Nature of the Insulator–Metal Transition of the Surface Layer
An Operando Study of the Thermal Reduction of BaTiO3 Crystals: The Nature of the Insulator–Metal Transition of the Surface Layer
The insulator-to-metal transition upon the thermal reduction of perovskites is a well-known yet not completely understood phenomenon. By combining different surface-sensitive analysis techniques, we analyze the electronic transport properties, electronic structure, and chemical composition during th...
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Personal Name(s): | Rodenbücher, Christian (Corresponding author) |
---|---|
Bihlmayer, Gustav / Korte, Carsten / Rytz, Daniel / Szade, Jacek / Szot, Kristof | |
Contributing Institute: |
Quanten-Theorie der Materialien; PGI-1 Elektrochemische Verfahrenstechnik; IEK-14 |
Published in: | Crystals, 13 (2023) 8, S. 1278 - |
Imprint: |
Basel
MDPI
2023
|
DOI: |
10.3390/cryst13081278 |
DOI: |
10.34734/FZJ-2023-03389 |
Document Type: |
Journal Article |
Research Program: |
Topological Matter |
Link: |
OpenAccess |
Publikationsportal JuSER |
Please use the identifier: http://dx.doi.org/10.34734/FZJ-2023-03389 in citations.
The insulator-to-metal transition upon the thermal reduction of perovskites is a well-known yet not completely understood phenomenon. By combining different surface-sensitive analysis techniques, we analyze the electronic transport properties, electronic structure, and chemical composition during the annealing and cooling of high-quality BaTiO3 single crystals under ultra-high-vacuum conditions. Our results reveal that dislocations in the surface layer of the crystal play a decisive role as they serve as easy reduction sites. In this way, conducting filaments evolve and allow for turning a macroscopic crystal into a state of metallic conductivity upon reduction, although only an extremely small amount of oxygen is released. After annealing at high temperatures, a valence change of the Ti ions in the surface layer occurs, which becomes pronounced upon the quenching of the crystal. This shows that the reduction-induced insulator-to-metal transition is a highly dynamic non-equilibrium process in which resegregation effects in the surface layer take place. Upon cooling to the ferroelectric phase, the metallicity can be preserved, creating a “ferroelectric metal.” Through a nanoscale analysis of the local conductivity and piezoelectricity, we submit that this phenomenon is not a bulk effect but originates from the simultaneous existence of dislocation-based metallic filaments and piezoelectrically active areas, which are spatially separated. |