The fate of aluminium in (Na,Bi)TiO3-based ionic conductors
The fate of aluminium in (Na,Bi)TiO3-based ionic conductors
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DOI：
10.1039/d0ta03554h
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发表时间：
2020-09
影响因子：
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通讯作者：
P. Groszewicz;L. Koch;S. Steiner;A. Ayrikyan;K. Webber;T. Frömling;K. Albe;G. Buntkowsky
中科院分区：
文献类型：
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作者：
P. Groszewicz;L. Koch;S. Steiner;A. Ayrikyan;K. Webber;T. Frömling;K. Albe;G. Buntkowsky
受体掺杂时形成相关缺陷（例如[AlTi-VO]）通常被视为钙钛矿离子导体中捕获移动的空位和压电钙钛矿中机电硬化的原因。为了阐明Al掺杂的（Na 1/2，Bi 1/2）TiO 3（NBT-Al）和Al取代的（（Na，K）1/2Bi 1/2）TiO 3-BiAlO 3（NKBT-BA）中相关缺陷的存在，我们采用阻抗谱、~（27）Al NMR谱和电子结构计算相结合的方法。我们的研究结果表明，只有在低受主掺杂浓度的情况下，才能发现和氧空位之间的相关缺陷。这表明在高掺杂浓度下缺陷缔合的驱动力降低，这是NBT基陶瓷的受主浓度和氧离子电导率之间的非线性依赖性的原因。此外，实验和理论技术的结合提供了明确的证据，连续占领的B-网站，A-网站，并最终形成的第二相与Al 3+含量的增加。总而言之，这些结果要求对异价掺杂剂与掺杂受体的功能氧化物中的O2-空位之间的相互作用进行新的评估，并对离子导体和铁电材料的设计产生影响。
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 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.