Synthesis and thermal reactions of rhabdophane- (Y).

Abstract

Syntheses of rhabdophane-(Y) (hexagonal YPO4·nH2O (n=0.5 to 1) were carried out by precipitation from aqueous solutions of Y(NO3)3·6H2O, (NH4)2HPO4 and citric acid with the mixing mole ratios of (NH4)2HPO4/Y(NO3)3·6H2O=4 and citric acid/Y(NO3)3·6H2O (C/Y)=5 to 30. Rhabdophane was obtained when those solutions were maintained at 90°C in the pH range 3 to 7 for 1 day to 30 days. Chemical formula and lattice constants of the well crystallized single phase rhabdophane obtained by the reaction at pH 7 and C/Y ratio 30 for 30 days were YPO4·0.6H2O, a=0.683 nm and c=0.630 nm, respectively. The hydrated rhabdophane was dehydrated at 180° to 250°C in air. Thereafter, no significant changes in crystal structure were seen up to 800°C. The water corresponding to 0.6H2O was zeolitic water. Anhydrous rhabdophane gradually changed to the xenotime structure above 900°C in air.