Complex Structural Disorder in a Polar Orthorhombic Perovskite Observed through the Maximum Entropy Method/Rietveld Technique
Complex Structural Disorder in a Polar Orthorhombic Perovskite Observed through the Maximum Entropy Method/Rietveld Technique
复制标题
通过最大熵法/Rietveld 技术观察极性正交钙钛矿中的复杂结构无序
DOI：
10.1021/acs.chemmater.1c01979
复制
发表时间：
2021
影响因子：
8.6
通讯作者：
Manjón-Sanz A
中科院分区：
文献类型：
--
作者：
Manjón-Sanz A
在环境压力下稳定的钙钛矿氧化物中，所有的Bi3+都在a位上是罕见的，已知的例子只有四个。由于Bi3+上的孤对，这些材料被视为在社会上广泛使用的基于pb的压电材料的最佳替代品。工业标准压电Pb (Zr1 -xTix)O3依赖于PbTiO3的[001]极化，但目前还没有具有这种极化矢量的环境压力稳定的bi基钙钛矿，因此无法创建类似的系统。我们对（1 -x）Bi (Ti3/8Fe2/8Mg3/8) O3-xCaTiO3的正交相进行了完整的结构分析，该正交相以pna21对称晶化，具有[001]极化。这种对称性是罕见的，在环境条件下钙钛矿只报道过两次。利用同步辐射粉末x射线衍射对最大熵法（MEM）模型进行分析，揭示了一种无序的a位结构，MEM/Rietveld技术生成了这种极端无序的结构模型。结合对x射线和中子衍射数据的Rietveld分析，我们可以准确地描述局域位置的结构，我们用它来理解我们的介电、铁电和压电测量。这些结果为如何稳定这种独特的对称性提供了见解，并激发了铋基压电材料的新设计原则。
Ambient pressure stable perovskite oxides with all Bi3+on theA-site are rare, with only four examples known. Due to the lone pair on Bi3+, these materials are seen as the best alternative to Pb-based piezoelectrics, which are used widely in society. The industry standard piezoelectric, Pb (Zr1 –xTix)O3, relies on the [001] polarization of PbTiO3, but there are currently no ambient pressure stable Bi-based perovskites with this polarization vector, preventing the creation of an analogous system. We present the full structural analysis of the orthorhombic phase of (1 –x)Bi (Ti3/8Fe2/8Mg3/8)O3–xCaTiO3, which crystallizes inPna21symmetry with [001] polarization. This symmetry is rare and has only been reported twice for perovskites at ambient conditions. Analysis of maximum entropy method (MEM) models using synchrotron radiation powder X-ray diffraction reveals a disorderedA-site configuration, and the MEM/Rietveld technique generates a structural model of this extreme disorder. Combined Rietveld analysis of X-ray and neutron diffraction data yields an accurate description of the localA-site configuration, which we use to understand our dielectric, ferroelectric, and piezoelectric measurements. These results give insight into how to stabilize this unique symmetry and inspire new design principles for Bi-based piezoelectrics.