Sintering of hydroxyapatite lath-like powders

Hydroxyapatite powders, which consisted of lath-like single-crystalline particles, were calcined at two different temperatures. Green and calcined powders were used for sintering HAp ceramic samples under uniaxial pressing. Powders and sintered samples were studied using various analytical techniques in order to determine how calcination affects the particle properties and the sintering behavior of HAp powders. It was found that calcination decreases the particles length and changes the particles morphology from lath-like to spherical shape. The relative density increases with increasing calcination temperature and aging time. It was found that long aging time favor the formation of thermally stable HAp particles, whereas a shorter one results in the formation of β-calcium phosphate during thermal treatment. Sintering of compacted powders begins at temperatures greater than 900°C, with a trend to increase the onset temperature as the calcination temperature is increased.