Synthesis and structure of alkali metal zirconium vanadate phosphates

Mixed vanadate phosphates in the systems MZr2(VO4) (x) (PO4)(3 - x) , where M is an alkali metal, were synthesized and studied by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Substitutional solid solutions with the structure of the mineral kosnarite (NZP) are formed at the compositions 0 a parts per thousand currency sign x a parts per thousand currency sign 0.2 for M = Li; 0 a parts per thousand currency sign x a parts per thousand currency sign 0.4 for M = Na; 0 a parts per thousand currency sign x a parts per thousand currency sign 0.5 for M = K; 0 a parts per thousand currency sign x a parts per thousand currency sign 0.3 for M = Rb; and 0 a parts per thousand currency sign x a parts per thousand currency sign 0.2 for M = Cs. Apart from the high-temperature NZP modification, lithium vanadate phosphates LiZr2(VO4) (x) (PO4)(3 - x) with 0 a parts per thousand currency sign x a parts per thousand currency sign 0.8 synthesized at temperatures not exceeding 840A degrees C crystallize in the scandium tungstate type structure. The crystal structures of LiZr2(VO4)(0.8)(PO4)(2.2) (space group P2(1)/n, a = 8.8447(6) , b = 8.9876(7) , c = 12.3976(7) , beta = 90.821(4)au <, V = 985.4(1) (3), Z = 4) and NaZr2(VO4)(0.4)(PO4)(2.6) (space group = 8.8182(3) , c = 22.7814(6) , V = 1534.14(1) (3), Z = 6) were refined by the Rietvield method. The framework of the vanadate phosphate structure is composed of tetrahedra (that are statistically occupied by vanadium and phosphorus atoms) and ZrO6 octahedra. The alkali metal atoms occupy extra-framework sites.