Effect of calcination on sintering of hydroxyapatite.

Four different temperatures (700-1000 degrees C) were chosen for calcination treatment of as-received hydroxyapatite powder before press forming and sintering to study the effect of calcination on the sintering behaviours. The results show that calcination treatment increases the average particle size and distribution, which changes from trimodal to monomodal. The sintering behaviours were investigated by dilatometry and density measurement. Fluidity of powder and driving force for sintering were found to dominate the properties. Calcining at 900 degrees C and sintering 1250 degrees C results in a higher bending strength (about 55 MPa) with finer grain size.