Two homologous new mixed‐metal phosphates K₂PbBi₂(PO₄)₂(P₂O₇) (I) and Rb₂CdBi₂(PO₄)₂(P₂O₇) (II) were successfully synthesized in A₂BBi₂(PO₄)₂(P₂O₇) (A = K, Rb, B = Pb, Cd) system through the traditional high‐temperature solid‐phase method. The single crystal structures of the two compounds are shown to be the unique three‐dimensional (3D) framework composed of different types of layers, but not isomorphic. We compared series compounds A₂PbBi₂(PO₄)₂(P₂O₇) (A = K, Rb, Cs), which are isomorphic and crystallize in the same space group Pnma. It is noteworthy that they are distinct different in degree of structural disorder, which is tuned by A‐site cations. The effect of A‐site cations is recognized by analyzing the disorder degree in three related structures and other available 182 mixed‐metal phosphates. To the best of our knowledge, such structural analysis is rarely reported in inorganic phosphates and the cation modulation strategy can be used to guide structural disorder according to the difference‐value (D‐value) of cation radii. Furthermore, the syntheses, thermal analysis, relevant spectroscopic measurements and theoretical calculations for I and II compounds were also discussed.

中文翻译：

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A2BBi2（PO4）2（P2O7）（A = K，Rb，B = Pb，Cd）：阳离子大小对结构演化的影响

在A ₂中成功合成了两种同源的新型混合金属磷酸盐K ₂ PbBi ₂（PO ₄）₂（P ₂ O ₇）（I）和Rb ₂ CdBi ₂（PO ₄）₂（P ₂ O ₇）（II）。BBi ₂（PO ₄）₂（P ₂ O ₇）（A = K，Rb，B = Pb，Cd）系统通过传统的高温固相方法。两种化合物的单晶结构显示为独特的三维（3D）框架，由不同类型的层组成，但不是同构的。我们比较了系列化合物A ₂ PbBi ₂（PO ₄）₂（P ₂ O ₇）（A = K，Rb，Cs），它们在同一个空间群Pnma中是同构并结晶的。值得注意的是，它们在结构紊乱程度上有明显不同，这是由A位阳离子调节的。通过分析三个相关结构和其他可用的182种混合金属磷酸盐的无序度，可以识别A位阳离子的作用。据我们所知，这种结构分析很少在无机磷酸盐中报道，阳离子调节策略可用于根据阳离子半径的差值（D值）指导结构紊乱。此外，还讨论了I和II化合物的合成，热分析，相关的光谱测量和理论计算。