Characterization of sol-gel derived zirconia with additions of yttria and ceria. Origin of high fracture toughness in ceria-stabilized samples

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Abstract
Fine powders of ZrO2 containing cubic or tetragonal phases in the systems Y2O3-ZrO2 and CeO2—ZrO2 have been prepared using the sol-gel technique without the addition of any catalysts. The powders have been compacted and either sintered at 1823 K or hot isostatic pressed (HIPed) at 1723 K (1h) under a pressure of 140 MPa (argon atmosphere). The sintered and HIPed samples have been examined for the fracture toughness (KIC) and biocompatibility. The KIC values ranged from 7–12 MPa m1/2 and all the samples have been found to exhibit a good biocompatibility. Formation of Ce2Zr2O7 (pyrochlore) in the case of 15Ce-TZP/HIPed sample has been interpreted using a chemical reaction which is very likely to be a spinoidal decomposition. The high value of KIC observed in 15Ce-TZP/HIPed has been rationalized by a probable decomposition of pyrochlore during crack propagation.