Structural investigation of the temperature-stable relaxor dielectric Ba0.8Ca0.2TiO3-Bi(Mg0.5Ti0.5)O3
Structural investigation of the temperature-stable relaxor dielectric Ba0.8Ca0.2TiO3-Bi(Mg0.5Ti0.5)O3
复制标题
DOI：
10.1016/j.jeurceramsoc.2022.09.039
复制
发表时间：
2022-09
影响因子：
5.7
通讯作者：
M. Cabral;A. Brown;J. Bultitude;A. Britton;R. Brydson;T. Roncal-Herrero;D. Hall;S. J. Milne;A. Rappe;D. Sinclair;J. Zhang;Y. Li
中科院分区：
文献类型：
--
作者：
M. Cabral;A. Brown;J. Bultitude;A. Britton;R. Brydson;T. Roncal-Herrero;D. Hall;S. J. Milne;A. Rappe;D. Sinclair;J. Zhang;Y. Li
用像差校正的扫描电子显微镜和电子衍射仪研究了Ca改性的Ba-₀.₈-Ca-₀.₂-Ti-₃-Bi(Mg-₀.₅-Ti₀.₅)O-₃弛豫介质陶瓷的局域结构和纳米化学性质，该陶瓷在较宽的温度范围内具有较高的和接近不变的相对介电常数。高分辨率的同步加速器X射线衍射仪显示了球形立方结构(Pm3m)，但STEM的直接原子尺度成像显示了局部的四方扭曲。从B位原子相对于氧离子位置沿积分微分相对比扫描电子显微镜图像的<； 100 &> 和<； 110 &> 区轴测量的纳米极团簇，突出显示团簇尺寸为2-5 nm。STEM-能量色散X射线光谱分析和X射线粉末衍射数据的全图样修正都表明，在基质中存在高水平的铋空位。讨论了这类介电材料中A位空位调制纳米极结构和促进介电温度响应平坦化的可能性。
Aberration corrected scanning transmission electron microscopy (STEM) and electron diffraction have been used to disclose local structure and nano-chemistry in a Ca modified Ba₀.₈Ca₀.₂TiO₃-Bi(Mg₀.₅Ti₀.₅)O₃ relaxor dielectric ceramic which exhibits high and near-invariant relative permittivity over a wide temperature range. High-resolution, synchrotron X-ray diffraction indicated a globally cubic structure (Pm3m), but direct atomic-scale imaging by STEM revealed local tetragonal distortions. Nanopolar clusters were identified from B-site atomic displacement vectors measured relative to oxygen ion positions along < 100 > and < 110 > zone axes of integrated differential phase contrast (iDPC) STEM images, highlighting cluster sizes of 2–5 nm. Chemical analysis by STEM-energy dispersive X-ray spectroscopy and full pattern refinements of X-ray powder diffraction data each implied high levels of Bi vacancies within the matrix. The possibility that these A-site vacancies modulate the nanopolar structure and promote flattening of the permittivity-temperature response in this class of dielectric is discussed.