Sintering of partially-stabilized zirconia and partially-stabilized zirconia-hydroxyapatite composites by hot isostatic pressing and pressureless sintering.

In this study two sintering techniques, pressureless sintering (PS) and hot isostatic pressing (HIP), were used for comparing the sinterability of two yttria-partially-stabilized zirconia/hydroxyapatite (PSZ/HA) composites. Virtually dense ceramics were obtained using HIP at a maximum pressure of 160 MPa for 1 h at 1225 degrees C for both PSZ powders and their HA composites. The ceramic bodies, produced using PS at the same temperature as in the HIP process and higher, had densities from 80% to 97% of theoretical density, depending on the properties of the PSZ powders. FTIR spectra of composites sintered by HIP and PS at 1225 degrees C were compared, indicating a degradation of HA by PS but no degradation by HIP. The bending strength of HIPed ceramics was measured and found to be high. It is concluded that it is possible to produce dense PSZ/HA composites by the HIP or PS processes. For the PS, the reactivity of powders is the key factor during the densification. The HIP technique is the preferable technique for producing stable and dense HA-containing composites.