A Detailed Study of the Dehydration Process in Synthetic Strelkinite, Na[(UO2)(VO4)]nH2O (n = 0, 1, 2)

Synthetic strelkinite Na[(UO2)(VO4)] center dot nH(2)O (n = 0, 1, 2) was systematically investigated by single crystal X-ray diffraction and thermoanalytical methods. The anhydrous form and two hydrates were isolated as single crystals and the structures of these phases solved: Na[(UO2)(VO4)], monoclinic, P2(1)/c, a = 6.0205(1) angstrom, b = 8.3365(1) angstrom, c = 10.4164(2) angstrom, beta = 100.466(2)degrees, V = 514.10(1) angstrom(3), R-1 = 0.0337; Na[(UO2)(VO4)] center dot H2O, monoclinic, P2(1)/c, a = 7.722(2) angstrom, b = 8.512(1) angstrom, c = 10.480(4) angstrom, beta = 113.18(3)degrees, V = 633.3(3) angstrom(3), R-1 = 0.1658; Na[(UO2)(VO4)] center dot 2 H2O, monoclinic, P2(1)/n, a = 16.2399(5) angstrom, b = 8.2844(2) angstrom, c = 10.5011(2) angstrom, beta = 97.644(2)degrees, V = 1400.24(6) angstrom(3), R-1 = 0.0776. A possible mechanism of the structural transformation processes during dehydration is proposed based on the structures of the anhydrous phase and the hydrates