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8H–10H Stacking Periodicity Control in Twinned Hexagonal Perovskite Dielectrics
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2018-03-19 00:00:00 , DOI: 10.1021/acs.inorgchem.8b00296 Weiwei Cao 1 , Xiaoyan Yang 1 , Fengqi Lu 1 , Wenfeng Zhu 1 , Laijun Liu 1 , Xiaojun Kuang 1 , Mathieu Allix 2, 3
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2018-03-19 00:00:00 , DOI: 10.1021/acs.inorgchem.8b00296 Weiwei Cao 1 , Xiaoyan Yang 1 , Fengqi Lu 1 , Wenfeng Zhu 1 , Laijun Liu 1 , Xiaojun Kuang 1 , Mathieu Allix 2, 3
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Isovalent substitution of Zr4+ for smaller Ti4+ was performed in the 8-layer twinned hexagonal perovskite (referred to as 8H) tantalate Ba8Ti3Ta4O24, which stabilizes a 10-layer twinned hexagonal perovskite (referred to as 10H). The formation of the 10H phase occurs at low substitution concentration (x = 0.1) in Ba8ZrxTi3–xTa4O24 at 1300 °C and reverts back to the 8H phase upon heating at elevated temperatures. Such a 10H-to-8H phase transformation is suppressed at higher Zr-substitution contents (x > 0.1). The approach combining simulated annealing and Rietveld refinement with compositional constrain indicates that the 10H Ba8Zr0.4Ti2.6Ta4O24 (x = 0.4) composition adopts a simply P63/mmc disordered structure with Zr cations preferably located in corner-sharing octahedral (CSO) sites compared to face-sharing octahedral (FSO) sites. This 8H-10H phase competition, dependent on the substitution of Zr4+ for Ti4+ and firing temperature, is discussed in terms of the FSO B–B repulsion controlled by the cationic size, as well as the stacking periodicity which affects the thermodynamic stability. Both 8H- and 10H-phase pellets of Ba8ZrxTi3–xTa4O24 exhibit comparable and poorer microwave dielectric properties than the parent 8H Ba8Ti3Ta4O24, which is characterized by cationic disorder and FSO B–B repulsion. The 8H and 10H Ba8ZrxTi3–xTa4O24 ceramics display electrical insulator behavior but with electrically heterogeneous microstructure on the bulk grains. This study demonstrates the opportunity to control the stacking periodicity for the twinned hexagonal perovskites via tuning the B-cationic size and the firing temperature.
中文翻译：
孪生六角形钙钛矿介质中的8H–10H堆叠周期控制
的Zr等价取代4+对于较小的Ti 4+中的8层进行联动六边形钙钛矿（简称8H）钽的Ba 8的Ti 3的Ta 4 ø 24，其稳定10层联动六边形钙钛矿（被称为10H）。10H相的形成在1300°C的Ba 8 Zr x Ti 3– x Ta 4 O 24中以低取代浓度（x = 0.1）发生，并在升高的温度加热时恢复为8H相。在较高的Zr取代含量下，这种10H至8H的相变受到抑制（x> 0.1）。将模拟退火和Rietveld精细化与成分约束相结合的方法表明，10H Ba 8 Zr 0.4 Ti 2.6 Ta 4 O 24（x = 0.4）成分采用简单的P 6 3 / mmc无序结构，且Zr阳离子优选位于拐角共享中。八面体（CSO）网站与面部共享八面体（FSO）网站相比。此8H-10H相竞争取决于Zr 4+替代Ti 4+根据阳离子大小控制的FSO B–B排斥力以及影响热力学稳定性的堆积周期，讨论了燃烧温度和烧成温度。与母体8H Ba 8 Ti 3 Ta 4 O 24相比，Ba 8 Zr x Ti 3– x Ta 4 O 24的8H和10H相微球均具有可比且较差的微波介电性能，其特征在于阳离子无序和FSO B –B排斥。8H和10H Ba 8 Zr x Ti 3– x Ta 4 O 24陶瓷表现出电绝缘体的行为，但在大颗粒上具有电异质的微观结构。这项研究表明有机会通过调节B-阳离子的大小和烧成温度来控制孪晶六方钙钛矿的堆积周期。
更新日期：2018-03-19
中文翻译：
孪生六角形钙钛矿介质中的8H–10H堆叠周期控制
的Zr等价取代4+对于较小的Ti 4+中的8层进行联动六边形钙钛矿（简称8H）钽的Ba 8的Ti 3的Ta 4 ø 24，其稳定10层联动六边形钙钛矿（被称为10H）。10H相的形成在1300°C的Ba 8 Zr x Ti 3– x Ta 4 O 24中以低取代浓度（x = 0.1）发生，并在升高的温度加热时恢复为8H相。在较高的Zr取代含量下，这种10H至8H的相变受到抑制（x> 0.1）。将模拟退火和Rietveld精细化与成分约束相结合的方法表明，10H Ba 8 Zr 0.4 Ti 2.6 Ta 4 O 24（x = 0.4）成分采用简单的P 6 3 / mmc无序结构，且Zr阳离子优选位于拐角共享中。八面体（CSO）网站与面部共享八面体（FSO）网站相比。此8H-10H相竞争取决于Zr 4+替代Ti 4+根据阳离子大小控制的FSO B–B排斥力以及影响热力学稳定性的堆积周期，讨论了燃烧温度和烧成温度。与母体8H Ba 8 Ti 3 Ta 4 O 24相比，Ba 8 Zr x Ti 3– x Ta 4 O 24的8H和10H相微球均具有可比且较差的微波介电性能，其特征在于阳离子无序和FSO B –B排斥。8H和10H Ba 8 Zr x Ti 3– x Ta 4 O 24陶瓷表现出电绝缘体的行为，但在大颗粒上具有电异质的微观结构。这项研究表明有机会通过调节B-阳离子的大小和烧成温度来控制孪晶六方钙钛矿的堆积周期。
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