Synthesis and thermal reactions of rhabdophane-(Yb or Lu)

Abstract

Poorly crystalline rhabdophane-(Yb or Lu) was synthesized by precipitation from mixed aqueous solutions of Ln(NO 3) 3 (Ln = Yb or Lu), (NH 4) 2HPO 4, and citric acid with the mixing mole ratios of (NH 4) 2HPO 4/Ln(NO 3) 3 = 4 and citric acid/Ln(NO 3) 3 = 5 to 30, at pH 7 and 90°C for 7 to 30 days. However, unknown XRD peaks and C–O bond FTIR absorption peaks were observed for the precipitates. These peaks disappeared with increasing heating temperature up to 400°C in air, and single phase rhabdophane-(Yb or Lu) was obtained when heated at 400 to 800°C in air. Chemical formulas of the single phase rhabdophane were YbPO 4·0.4H 2O and LuPO 4·0.5H 2O, respectively. The water corresponding to 0.4H 2O (or 0.5H 2O) was zeolitic water. The lattice constants are a = 0.676 and c = 0.626 nm for Yb, and a = 0.674 and c = 0.630 nm for Lu. Rhabdophane-(Yb or Lu) changed into the xenotime structure above 860°C, which was stable even at 1800°C in air.