Thermal stability and mechanical properties of zirconia–hydroxyapatite composites

Abstract

Yttria stabilised zirconia composites doped with different contents of hydroxyapatite were prepared by treatments including ball milling, cold isostatic pressing and sintering in air. The phase compositions of the composite ceramics were characterised by X-ray diffraction, and the effects of sintering temperatures and the quantity of hydroxyapatite on the phase compositions and mechanical properties of the composite ceramics were also analysed. The results showed that the hydroxyapatite decomposes into calcium oxide and beta tricalcium phosphate at high temperatures, and the cubic and monoclinic zirconia were formed from the tetragonal zirconia by combining the resultant CaO decomposed from hydroxyapatite. As a result, the composite ceramics are mainly composed of tetragonal zirconia and monoclinic zirconia, and interspersed with a small quantity of cubic zirconia and calcium phosphate. It was also found that the content of monoclinic zirconia increased with the increase in hydroxyapatite. There was no linear relationship between the amount of hydroxyapatite in the composites and the mechanical properties. The addition of hydroxyapatite and monoclinic zirconia content is the key to affect the mechanical properties of composites.