Synthesis and thermal behaviour of β tricalcium phosphate precipitated from aqueous solutions

Abstract In the present study, β tricalcium phosphate (β-TCP) was prepared by precipitation from aqueous solutions. Calcium nitrate tetrahydrate Ca(NO3)2.4H2O and diammonium hydrogen phosphate (NH4)2HPO4 salts with an initial Ca/P molar ratio of 1·5 were dissolved in distilled water and mixed at 20°C and pH 10. Phase evolution of the as received precipitate was studied by X-ray diffraction and infrared spectroscopy before and after calcination in a dry air atmosphere at temperatures in the range 200-1400°C for 1 h. Thermal behaviour was investigated by simultaneous thermal analysis (DTA-TG). Calcium and phosphorus contents of the as received precipitate were determined by the inductively coupled plasma technique, and a Ca/P molar ratio of 1·49 ± 0·01 was found. The densities of the as received precipitate and of powder calcined at 800°C were determined by picnometery to be 2·43 and 3·01 ± 0·05 g cm-3 respectively. The experimental data suggest the formation of an amorphous phase corresponding to a TCP-like composition, which is calcium deficient and contains a very small amount of HPO42- groups.

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