Modulated phases in the Ba2SiO4-Ca2SiO4 system of A2BX4, K2SO4-related structures
Modulated phases in the Ba2SiO4-Ca2SiO4 system of A2BX4, K2SO4-related structures
复制标题
DOI：
10.1080/08893118908032945
复制
发表时间：
1989-03
影响因子：
3
通讯作者：
R. Withers;J. G. Thompson;B. Hyde
中科院分区：
文献类型：
--
作者：
R. Withers;J. G. Thompson;B. Hyde
摘要 A2BX4 家族的 K2SO4 相关结构长期以来一直受到晶体化学家的关注，这主要是因为它们有时表现出许多不同的多晶型物和复杂的相变序列，随温度变化。对于大多数此类 A2BX4 化合物，本质上只有两种不同的结构类型或母体结构 - 与 α-K2SO4 同晶的高温“六方”形式和与 β-K2SO4 同晶的低温斜方晶形式。然而，除了这两种原型结构之外，还经常存在弱扭曲或调制的变体。就 Ba2-xCaxSiO4 系统而言，通过电子衍射研究和表征发现了五种此类调制变体。与弱卫星反射相关的特征卫星消光条件已被用来确定与每个观测到的调制波矢量相关的位移特征向量和原子位移模式。广泛发生的...
Abstract The A2BX4 family of K2SO4-related structures have long been of interest to crystal chemists, largely due to the numerous different polymorphs and complicated sequences of phase transitions they sometimes exhibit as a function of temperature. For most such A2BX4 compounds, there are essentially only two distinct structure types or parent structures — a high-temperature, ‚hexagonal‘ form isomorphous to α-K2SO4 and a lower-temperature, orthorhombic form isomorphous to β-K2SO4. In addition to these two prototype structures, however, there often exist weakly distorted, or modulated, variants. In the case of the Ba2-xCaxSiO4 system, five such modulated variants have been found via an electron diffraction study and characterized. The characteristic satellite extinction conditions associated with the weak satellite reflections have been used to determine displacement eigenvectors and atomic displacement patterns associated with each of the observed modulation wave-vectors. The widespread occurrence of mo...