Zirconia–fluorapatite materials produced by HIP

Composites of tetragonal zirconia and fluorapatite were sealed in steel tubes and hot isostatically pressed at 1200°C. The phases formed in the samples were evaluated by X-ray powder diffraction. When the composites contained larger amounts of fluorapatite, the tetragonal zirconia changed gradually into the cubic phase with decreasing zirconia content. These phase changes occurred due to a transfer of calcium from fluorapatite, which acted as an additional dopant in zirconia. Small amounts of monoclinic zirconia were also present in all samples. The cell dimension in fluorapatite was changed with the composition of the composite. However, decomposition of the fluorapatite was not possible to detect. Vickers hardness and fracture toughness were measured and ranged from 5.1 to 10.8 GPa and 0.9–5.5 MPam1/2, respectively. Microstructures in the composites were studied with scanning electron microscopy.