The effect of temperature on the properties of hydroxyapatite precipitated from calcium hydroxide and phosphoric acid

The effect of temperature on stoichiometry, morphology and crystallinity of hydroxyapatite (HA) prepared from calcium hydroxide and phosphoric acid was investigated. The crystals precipitated in the temperature range 22–95°C and matured for 20 h at precipitation temperature have shown the properties of thermally stable HA. The size and crystallinity of the crystals increase with an increase of the preparation temperature. HA precipitated at 95°C shows thermal stability even without ripening. The importance of the maturation stage in obtaining thermally stable HA increases with decreasing precipitation temperature. HA precipitated at low temperature (22°C) after appropriate maturation shows the properties of stoichiometric low crystalline HA and appears to be very promising as a bioceramic precursor.