THERMAL-BEHAVIOR OF CADMIUM-CONTAINING APATITES

The behaviour of cadmium hydroxy- and fluorapatites at 500-1000°C and under low or high water vapor pressure were examined by X-ray diffraction and IR spectrometry. Heat treatment induces decomposition of both hydroxyapatites and fluorapatites. The decomposition temperature and the nature of the crystalline phases (cadmium oxide, tetracadmium phosphate, trimetallic phosphate) are strongly dependent on water vapor pressure and the nature and cadmium content of the initial compounds. Fluorapatites appear to be more stable than hydroxyapatites; a cadmium rate increase destabilizes the apatitic structure and high water vapor pressure stabilizes the hydroxyapatites. © 1993 Academic Press, Inc.