Chemical preparation and thermal behavior of neodymium cyclotriphosphate pentahydrate NdP3O9·5H2O: A study by Controlled Rate Thermal Analysis (CRTA)

A new neodymium cyclotriphosphate pentahydrate powder, NdP3O9·5H2O, has been prepared using a classical chemistry method and characterized by X-ray diffraction and infrared spectroscopy techniques. The IR spectrum shows the characteristic bands of cyclotriphosphates as the triplet in the range 1055–1007–917 cm−1. The thermal behavior of the titled compound was also carried out using conventional thermal analysis techniques (TG and DSC) under air atmosphere and Controlled transformation Rate Thermal Analysis (CRTA) technique under constant water vapour pressure of 5 hPa. It was shown that thermal treatment in air, with linear heating rate of 10 K min−1, favourites the structure breakdown as soon as the release of water molecules starts. In this case an amorphous compound is obtained, which then crystallizes at 1073 K and gives the polyphosphate Nd(PO3)3. However, by CRTA technique at image, the water molecules are eliminated with a lower rate which permits to save the initial structure up to an advanced dehydration step. The breakdown of the initial structure is immediately followed by the crystallization of the anhydrous polyphosphate Nd(PO3)3 phase in the temperature range 455 K < T < 793 K.