The crystal structures of three polymorphs of K₃GaF₆ and the transition temperatures between these phases are reported for the first time. Synchrotron powder diffraction data clearly show that at 300 K α‐K₃GaF₆ crystallizes in space group I4₁/a with lattice parameters of a = 19.1124 (3) Å, c = 34.4165 (6) Å, and Z = 80. The structure is based on the double perovskite but with two fifths of the GaF₆ octahedra rotated by ∼45°. This phase remains stable until ∼460 K, above which it undergoes a transition to I4/m with lattice parameters of a = 13.6088 (4) Å, c = 8.6764 (3) Å, and Z = 10 at 485 K. β‐K₃GaF₆ has a similar structure but with only one fifth of the GaF₆ rotated by ∼45°. Above ∼510 K, the cubic Fm3m δ‐K₃GaF₆ structure is stabilized, with a lattice parameter of a = 8.6649 (1) Å at 550 K. The F atoms have highly anisotropic displacement parameters which suggest dynamic octahedral tilting is occurring. This work expands the fairly small group of double perovskite compounds which display non‐cooperative patterns of octahedral tilting.

中文翻译：

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双钙钛矿中非合作八面体倾斜的新例子：K3GaF6中的相变

首次报道了K ₃ GaF ₆的三种多晶型物的晶体结构和这些相之间的转变温度。同步加速器粉末衍射数据清楚地表明，在300 K α‐K ₃ GaF ₆的空间群I 4 ₁ / a中结晶，晶格参数为a = 19.1124（3）Å，c = 34.4165（6）Å，Z = 80。该结构基于双钙钛矿，但GaF ₆八面体的五分之二旋转了〜45°。此阶段一直保持稳定，直到〜460 K，在该阶段以上阶段过渡到I 4 / m用的晶格参数一个= 13.6088（4），C ^ = 8.6764（3）埃，ž 10在485 =βK.-K ₃ GAF ₆具有相似的结构，但只有五分之一的GAF ₆旋转了〜 45°。以上~510 K，立方FM 3米δ-K ₃ GAF ₆结构是稳定的，具有的晶格参数一个在550个K的F原子= 8.6649（1）埃具有高度各向异性位移参数，其表明动态八面体倾转发生。这项工作扩大了显示钙八面体倾斜的非合作模式的双钙钛矿化合物的相对较小的组。