ALiZnP2O7 (A = Rb, Cs): Two Mixed Alkali Zinc Pyrophosphates Featuring a [Li2Zn2P4O20]14– Anionic Skeleton

Two new isotypic diphosphates, RbLiZnP₂O₇ (RLZP) and CsLiZnP₂O₇ (CLZP), have been synthesized by a high-temperature solid-phase method. They both crystallize in the Pnma space group (No. 62) and have similar crystal configurations. ALiZnP₂O₇ (A = Rb, Cs) consists of a [Li₂Zn₂P₄O₂₀]^14- anionic skeleton, which is composed of Li/ZnO₄ tetrahedral and diphosphate groups, and the Rb or Cs atoms are located in the large hole. In this paper, we discuss the structures of the title compounds and isonomic AA'ZnP₂O₇ (A = alkali metal); it is found that the ionic radii of the cations and bond angles have an effect on the symmetry of the compounds. By analysis, we found that the M/P values have some effect on the dimensionality of the anionic groups in phosphates containing P₂O₇ groups. Thermal and spectral analyses are carried out on the title compounds. Besides that mentioned above, we also studied the relationship between the electronic structures and optical properties by theoretical calculations.