Phase Interactions in Monoclinic Zirconia Reinforced Hydroxylapatite Bioceramics

Hydroxylapatite composites with pure zirconia were prepared with pressureless air sintering and hot pressing for 1 hour at different temperatures between 900°C and 1300°C. The interaction between the phases was monitored with XRD and thermal analysis. At sintering temperatures higher than 1000°C, an apparent Ca diffusion occurred from hydroxylapatite to pure zirconia phase and changed its structure from monoclinic to tetragonal/cubic. In the mean time, hydroxylapatite decomposed and formed tricalcium phosphate. Also, a reaction was occurred at 1220°C between hydroxylapatite and zirconia phase forming CaZrO₃. The existence of air in the processing environment increased the reactivity between hydroxylapatite and zirconia.