Synthesis study of alkaline-bearing rare earth phosphates with rhabdophane structure

The synthesis mechanism of CsCaNd(PO4)2 from nitrates, carbonates and oxides of the different cations was investigated with the aim of immobilizing cesium. Two transitory phases, a monazite-type one, NdPO4, and a poorly crystallized cesium phosphate, CsCaPO4, were proposed to explain the formation of CsCaNd(PO4)2. Direct synthesis from NdPO4 and CsCaPO4 was thus carried out. It allowed to underline that within a 900-1000 °C temperature range the rhabdophane structure, CsCaNd(PO4)2, was formed. However, the reaction was also found to be incomplete and this was assumed to be due to a lack of reactivity in concern with the high stability of monazite.