Structural behavior, crystal chemistry, and phase transitions in substituted leucite: High-resolution neutron powder diffraction studies
Structural behavior, crystal chemistry, and phase transitions in substituted leucite: High-resolution neutron powder diffraction studies
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取代白榴石的结构行为、晶体化学和相变：高分辨率中子粉末衍射研究
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
B. M. Powell
中科院分区：
文献类型：
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作者：
D. Palmer;M. Dove;R. Ibberson;B. M. Powell
摘要 采用高分辨率中子粉末衍射研究了 KAlSi2O6、RbAlSi2O6、CsAlSi2O6 和 KFeSi2O6 的白榴石相的相变。温度依赖性结构行为涉及两种机制：通道阳离子四面体框架的弛豫，以及缓慢改变的 T-O 键长。高温立方相的特点是具有完全延伸的四面体骨架；热膨胀是通过平均 T-O 键长的增加而发生的。当温度降低时，向四方对称性的位移相变表现为光学不稳定性；角连接的 (Al,Si)O4 四面体的四方棱柱关于 [001] 的扭曲导致 <111> 结构通道的塌陷并伴随体积减小。
Abstract High-resolution neutron powder diffraction was used to study phase transitions in the leucite phases of KAlSi2O6, RbAlSi2O6, CsAlSi2O6, and KFeSi2O6. The temperature-dependent structural behavior involves two mechanisms: relaxation of the tetrahedral framework about channel cations, and slowly changing T-O bond lengths. The high-temperature cubic phase is characterized by a fully-extended tetrahedral framework; thermal expansion occurs by an increase in mean T-O bond lengths. On decreasing temperature, a displacive phase transition to tetragonal symmetry is manifested by an optic instability; twisting of tetragonal prisms of comer-linked (Al,Si)O4 tetrahedra about [001] leads to collapse of the 〈111〉 structural channels and concomitant volume reduction.