Community Research and Development Information Service - CORDIS

Development of a high purity zirconia material qualified for biomedical applications

Research was carried out into the development of a high purity yttria stabilized zirconia ceramic material, focussing especially to an extremely low level of radiochemical impurities, high mechanical strength, fracture toughness and excellent hydrothermal stability. The material was designed for biomedical applications as well as for other structural engineering and electronic applications. It was demonstrated that type B powders (yttria coated zirconia powders Y-TZP) show an excellent sintering behaviour even at very low sintering temperatures. During sintering a yttria gradient is formed, leading to excellent hydrothermal stability. It has been demonstrated that the strength loss after 120 hours of hydrothermal treatment (140 C, 0.2 MPa) in these materials only is about 10 %, while type A materials (zirconium salt and yttria salt are precipitated followed by calcination) showed a strength loss of 25 %. Cross sectioned parts did not show any corrosion effect for type B materials, while a significant corrosion of type A materials took place. Ageing of type B materials for 1 year in Ringer's at 37 °C did not show any strength loss or any corrosion. For final qualification of Y-TZP type B material in vitro test protocols have been established. It was demonstrated that low radioactivity material does not elicit and mutation and transformation effects on C3H10T(1/2) cells. Implantation of cylinders into femur, tibia and muscle according to ISO 10993 and UNI and EN 30993 macroscopical examination of lung, liver, kidney, spleen and heart showed that Y-TZP ceramics with extremely low radioactivity impurity levels are qualified for biomedical applications. A mechanical strength of 1150 MPa, a fracture toughness of 10 MPa vm and a hardness of HV(0.5) = 1250 has been measured in Y-TZP ceramics derived from yttria coated zirconia powders. Due to its excellent material properties hydrothermal stability and biocompatibility, a new processing route for Y-YZP has been established.

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