New Y-TZP powders for medical grade zirconia.

There is interest in using zirconia for biomedical applications as ball heads for total hip prostheses. Two potential types are under discussion: partially stabilized zirconia (PSZ) and tetragonal zirconia polycrystals (TZP) materials. Because of its enhanced material properties, TZP stabilized with yttria is favourable. To eliminate high amounts of natural radioactive impurities, the precursors are purified. The kind of precursor and purification method determine the powder impurity level. The disadvantage of Y-TZP is that the hydrothermal decomposition reaction method is that it depends very strongly on the grain size and the distribution of the stabilizing yttria within the zirconia grains. Thermodynamical and kinetic investigations on high purity coprecipitated and yttria-coated zirconia powders show different behaviours. Y-TZP materials based on yttria-coated zirconia powders show excellent mechanical strength of more than 1000 MPa, a Weibull modulus of up to 20 a! nd a fracture toughness of 9 MPa radical m. The material properties of Y-TZP ceramics based on coprecipitated powders and prepared under the same conditions are less attractive. It is expected that materials based on yttria-coated zirconia will show enhanced properties compared to materials derived from coprecipitated powders. Therefore Y-TZP materials derived from yttria-coated powders are very attractive as medical grade zirconia.