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

Abstract

Fine powders of $ZrO_2$ containing cubic or tetragonal phases in the systems $Y_2O_3-ZrO_2$ and $CeO_2-ZrO_2$ 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 (1 h) under a pressure of 140 MPa (argon atmosphere). The sintered and HIPed samples have been examined for the fracture toughness $(K_{IC})$ and biocompatibility. The $K_{IC}$ values ranged from 7-12 MPa $m^{1/2}$ and all the samples have been found to exhibit a good biocompatibility. Formation of $Ce_2Zr_2O_7$ (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 $K_{IC}$ observed in 15Ce-TZP/HIPed has been rationalized by a probable decomposition of pyrochlore during crack propagation.