Fabrication of Hydroxyapatite-incorporated ZrO2-20 wt% Al2O3 by Spark Plasma Sintering and Characterization

Yttria-stabilized tetragonal zirconia/20 wt% alumina (TZP-3Y20A) composites were fabricated by spark plasma sintering at various sintering temperatures over the range of 1000-1400 degrees C. Hydroxyapatite (HA) additive was added in volume fractions of 10-50% in order to increase the biocompatibility of the composite. The densification behavior of the TZP-3Y20A composite and that of the composites with HA were investigated. In the case of TZP-3Y20A composites, the density increases steadily with temperature and reaches a maximum value of 97.8% of the theoretical density at 1400 degrees C. The solution interface formed between zirconia (ZrO2) and alumina (Al2O3) strengthens the bond between ZrO2 and Al2O3 grains and facilitates densification. In the case of TZP-3Y20A/HA composites, sintering at 1400 degrees C led to the formation of tricalcium phosphate in the samples, which resulted from the decomposition of HA due to its limited thermal stability at high temperature; no reaction was observed between ZrO2 and HA. The addition of HA imposes a barrier effect on the diffusion between ZrO2 and Al2O3 grains, thus limiting the grain growth of ZrO2 and Al2O3.