Structure–property relationships were determined for the family of three-layer Aurivillius materials Bi₂Sr(A)TiNb₂O₁₂ (A = Ca²⁺, Sr²⁺, Ba²⁺). X-ray and neutron diffraction along with selected area electron diffraction indicate that Bi₂SrBaTiNb₂O₁₂ crystallizes in the nonpolar I4/mmm space group, whereas the polar B2cb space group best describes Bi₂SrCaTiNb₂O₁₂ and Bi₂Sr₂TiNb₂O₁₂. Despite the different space groups, all three compositions show relaxor behavior as evidenced through P(E) and dielectric measurements. These relaxor properties are derived from the extensive amount of disorder in each composition that is found at every cationic crystallographic site and do not depend on the space group. This disorder is so extensive that it disrupts the ferroelectric properties allowed by symmetry in the B2cb space group. This work demonstrates the important role of cation substitution and site disorder in these three-layered Aurivillius materials and its significant effect on both ferroelectric and dielectric properties.

中文翻译：

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高取代Bi ₂ Sr（A）TiNb ₂ O ₁₂（A = Ca 2 ⁺，Sr 2 ⁺，Ba ²⁺）Aurivillius相的介电和铁电性质

确定了三层Aurivillius材料Bi ₂ Sr（A）TiNb ₂ O ₁₂（A = Ca 2 ⁺，Sr 2 ⁺，Ba ²⁺）族的结​​构-性质关系。X射线和中子衍射以及选定的区域电子衍射表明，Bi ₂ SrBaTiNb ₂ O ₁₂在非极性I 4 / mmm空间群中结晶，而极性B 2 cb空间群最能描述Bi ₂ SrCaTiNb ₂ O ₁₂和Bi ₂锶₂ TiNb₂ O ₁₂。尽管空间组不同，但所有三种成分均表现出弛豫行为，这可通过P（E）和电介质测量来证明。这些松弛剂性质源自在每个阳离子晶体学位点发现的每种组合物中的大量无序，并且不依赖于空间基团。这种无序状态非常广泛，以至于破坏了B 2 cb空间群中对称性所允许的铁电性能。这项工作证明了阳离子取代和位错在这些三层Aurivillius材料中的重要作用及其对铁电和介电性能的显着影响。