IR study of the structure of rhombohedral zirconium and alkali metal orthophosphates

Zirconium orthophosphates with different alkali cations MZr₂(PO_{4 3}, M₂Zr(PO₄)₂, and M₅Zr(PO₄4)₃, where M is Na, K, Rb, Cs, were synthesized and studied by IR spectroscopy. X-ray diffraction, and ⁴⁰K radiometric analysis. It is confirmed that MZr₂(PO_{4 3} (M = Na, K, Rb, Cs) exist as rhombohedral phases crystallizing as NaZr₂(PO_{4 3}) (NZP) structures. For Na₅Zr(PO_{4 3} it is shown that an NZP phase with a monoclinic superstructure is formed as a result of statistical distribution of Na and Zr in the ZrO₆ octahedm and ordered distribution of sodium atoms in the interstices of the channels. Formation of K₂Zr(PO₄)₂ and K₅Zr(PO₄)₃ phases with NZP structures is shown to be possible. Translated from Zhumal Struktumoi Khimii, Vol. 41, No. 1, pp. 74-79, January-February, 2000.