Groszewicz, Pedro B. ; Koch, Leonie ; Steiner, Sebastian ; Ayrikyan, Azatuhi ; Webber, Kyle G. ; Frömling, Till ; Albe, Karsten ; Buntkowsky, Gerd (2020)
The fate of aluminium in (Na,Bi)TiO3-based ionicconductors.
In: Journal of Materials Chemistry A, 2020 (8)
doi: 10.1039/d0ta03554h
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

The formation of associated defects (e.g.[AlTi–VO]c) upon acceptor doping is commonly seen as a reasonfor trapping of mobile vacancies in perovskite ionic conductors and electromechanical hardening inpiezoelectric perovskites. In order to clarify the presence of associated defects in Al-doped (Na1/2,Bi1/2)TiO3(NBT–Al) and Al-substituted ((Na,K)1/2Bi1/2)TiO3–BiAlO3(NKBT–BA), we employ a combination ofimpedance spectroscopy,27Al NMR spectroscopy, and electronic structure calculations. Our resultsindicate that associated defects between Al0Tiand oxygen vacancies can only be found in case of lowacceptor doping concentrations. This suggests a decreased driving force for defect association at highdoping concentrations as the reason for the non-linear dependence between acceptor concentrationand oxygen ionic conductivity for NBT-based ceramics. Furthermore, the combination of experimentaland theoretical techniques provides clear evidence for the successive occupation of the B-site, the A-site, andfinally the formation of a secondary phase with increasing Al3+content. Altogether, these resultscall for a new evaluation of the interaction between aliovalent dopants and O2�vacancies in acceptor-doped functional oxides, with implications for the design of ionic conductors as well as ferroelectricmaterials.

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