[Spectral properties and thermal stability of zinc phosphate hydrate]

X-ray, FTIR, and Raman spectra were used to measure the spectral properties of three kinds of zinc phosphate hydrate. Spectral changes with crystalline water were analyzed. The thermal stability of zinc phosphate tetrahydrate was studied by TG-DTA to identify the existent temperature of zinc phosphate hydrate. The results show that the differences in crystalline water among these hydrates results in the variation in both 2theta characteristic values and peaks. The FTIR spectra reflect H--O--H strength information (1 600 cm(-1)) and O--H bond stretching vibrations (3 400-3 500 cm(-1)). Raman spectra show the difference in P--O bond stretching mode at 400-700 cm(-1) and the shape of O--H stretching peak. According to the mass-loss curves, the onset temperature of zinc phosphate tetrahydrate was 95 degrees C. Heating to 145 degrees C was accompanied by the removal of 2H2O and transform into Zn3 (PO4)2 x 2H2O, indicating that Zn3 (PO4)2 x 2H2O was established at this temperature. Zn3 (PO4)2 x H2O can be obtained by heating to 195 degrees C. The third stage of dehydration gave an anhydrous Zn3 (PO4)2 phase.