The thermal shock resistance of Y2O3 ceramics

Abstract Y 2 O 3 ceramics samples with various grain size were tested in non-symmetric thermal shock conditions in two methods. In the first test the samples were heated in a furnace up to the predetermined temperature (530 °C) and then the polished surfaces with Vickers indents were subjected to sudden temperature change using a high-velocity nitrogen jet at room temperature. The gas was channelled onto the disk centre for about 20 s. In the second test samples were quickly inserted into a hot furnace (850 °C). The polished surfaces with Vickers indents were sheltered by thick alumina disks. The length of surface cracks before and after thermal shocks were measured with an optical microscopy and then a parameter R m (an indicator of thermal stress resistance) was obtained. Hence the thermal stress σ T , which caused crack growth, was calculated using the value of fracture toughness K Ic . These stresses were similar for both shock cases (about 50 MPa) and they were not dependent on grain size of the ceramics.