The study of the crystalline phosphates of kosnarite type structure containing different alkali metals

The incorporation possibilities of different alkali elements into crystalline phosphates A1−xA′xHf2(PO4)3 (A=Li, Na, K, Rb, Cs) were studied, the formation regions of kosnarite solid solutions were determined. Na0.5K0.5Hf2(PO4)3 crystal structure was studied by powder X-ray diffraction, and the distribution of alkali metals in kosnarite structure was found out. The phosphate crystallizes in the space group R3̄c, with a=8.7295(1) Å, c=23.2023(4) Å, V=1531.24(4) Å3, Z=6; Rwp=6.15, Rp=4.43. The concentration region knowledge of the kosnarite phase existence and peculiarities of their phase formation in the A1−xA′xM2(PO4)3 (M=Ti, Zr, Hf) systems allow us to choose phosphate matrice compositions suitable for solidification of reprocessing wastes of spent U–Pu nuclear fuels.