New Y-TZP powders for medical grade zirconia

There is interest in using zirconia for biomedical applications as ballheads 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 withyttria is favourable. To eliminate high amounts of natural radioactiveimpurities, the precursors are purified. The kind of precursor and purificationmethod determine the powder impurity level. The disadvantage of Y-TZP is thatthe hydrothermal decomposition reaction method is that it depends very stronglyon the grain size and the distribution of the stabilizing yttria within thezirconia grains. Thermodynamical and kinetic investigations on high puritycoprecipitated and yttria-coated zirconia powders show different behaviours.Y-TZP materials based on yttria-coated zirconia powders show excellentmechanical strength of more than 1000 MPa, a Weibull modulus of up to 20 a!nd a fracture toughness of 9 MPa√m. The material properties of Y-TZP ceramicsbased on coprecipitated powders and prepared under the same conditions are lessattractive. It is expected that materials based on yttria-coated zirconia willshow enhanced properties compared to materials derived from coprecipitatedpowders. Therefore Y-TZP materials derived from yttria-coated powders are veryattractive as medical grade zirconia.