Filter cake forming and hot isostatic pressing for TZP-dispersed hydroxyapatite composite

The combination of a filter cake forming process and hot isostatic pressing was applied to prepare hydroxyapatite composites containing dispersed tetragonal zirconia polycrystal (TZP) with high strength and toughness. Fine TZP powder was dispersed into as-synthesized hydroxyapatite slurry, formed with the filter cake process and hot isostatically pressed at 800–1150 °C at 100 MPa for 2 h. The temperature needed for densification increased with increasing TZP content; 1100 °C was needed to fully densify the composite with 26.8 wt% TZP. No phase change was found in TZP nor in the hydroxyapatite phase up to the maximum temperature examined in hot isostatic pressing. Significant phase change was found in specimens annealed in air at 1200 °C. The strength and toughness achieved were respectively 190 MPa and 2.3 MPa m^1/2. These values were approximately 20% and 100% higher than the corresponding values for hydroxyapatite ceramics without TZP particle dispersion.