An alkali metal phosphate RbPbBi2(PO4)3 with three kinds of disorder: the effect of isolated soft cation units on the crystal structure

Abstract

With isolated Rb–O units and PO₄ tetrahedra, RbPbBi₂(PO₄)₃ exhibits three kinds of disorder in the crystal structure. Significantly, structures with isolated cation units like Cs–O, Rb–O and K–O units exhibit quite high ratios of disorder in inorganic phosphates. We firstly put forward the concept of isolated soft units that can cause structural distortions of the crystal structure and is favorable for the appearance of structural disorder. In addition, the synthesis, IR spectra, UV-vis-NIR diffuse reflectance spectroscopy data, and thermal and second harmonic generation (SHG) tests of the title compound have been reported.