Thermal shock resistance of yttria-stabilized zirconia with Palmqvist indentation cracks

Thermal shock behaviour of two tetragonal zirconia polycrystals stabilised with 2.5% molar yttria and with different fracture toughness have been investigated by analysing stable crack extension of indentation Palmqvist cracks in the quench indentation test. It is shown that the ratio between the thermal stress intensity factor and the fracture toughness can be easily obtained by measuring the stable crack extension. It is shown that deviations from the expected maximum stable crack extension during thermal shock can be accounted for by subcritical crack growth and by a reduction in the level of residual stresses. For small indentation loads, R-curve effects become important and must be considered to explain the experimental results.