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Issue 35, 2020
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The fate of aluminium in (Na,Bi)TiO3-based ionic conductors

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The formation of associated defects (e.g. [AlTi–VO]˙) upon acceptor doping is commonly seen as a reason for trapping of mobile vacancies in perovskite ionic conductors and electromechanical hardening in piezoelectric 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 of impedance spectroscopy, 27Al NMR spectroscopy, and electronic structure calculations. Our results indicate that associated defects between Image ID:d0ta03554h-t1.gif and oxygen vacancies can only be found in case of low acceptor doping concentrations. This suggests a decreased driving force for defect association at high doping concentrations as the reason for the non-linear dependence between acceptor concentration and oxygen ionic conductivity for NBT-based ceramics. Furthermore, the combination of experimental and theoretical techniques provides clear evidence for the successive occupation of the B-site, the A-site, and finally the formation of a secondary phase with increasing Al3+ content. Altogether, these results call 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 ferroelectric materials.

Graphical abstract: The fate of aluminium in (Na,Bi)TiO3-based ionic conductors

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Supplementary files

Article information

31 Mar 2020
13 Aug 2020
First published
14 Aug 2020

J. Mater. Chem. A, 2020,8, 18188-18197
Article type

The fate of aluminium in (Na,Bi)TiO3-based ionic conductors

P. B. Groszewicz, L. Koch, S. Steiner, A. Ayrikyan, K. G. Webber, T. Frömling, K. Albe and G. Buntkowsky, J. Mater. Chem. A, 2020, 8, 18188
DOI: 10.1039/D0TA03554H

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