Effects of Li₃PO₄ Addition on the Mechanism of Initial-stage Sintering of Hydroxyapatite

Abstract

The mechanism of the initial-stage sintering of the hydroxyapatite(HAP)containing Li₃PO₄ was investigated by using the constant-rate heating technique. For the HAP without additives, the rate-controlling mechanism below 800℃ was the grain -boundary diffusion characterized by the apparent activation energy of 104kcal/mol. For the HAP containing Li₃PO₄, the grain-boundary diffusion controlled the rate of the densification below 750℃.However, above 750℃, the sintering parameter N decreased from 1.9 to 0.6. This suggested that above 750℃ densification occurred by the rearrangement process with the liquid-phase. The calculation of the apparent activation energy value for the liquid sintering was 252kcal/mol.