Grain‐Size Dependence of Thermal‐Shock Resistance of Yttria‐Doped Tetragonal Zirconia Polycrystals

Thermal‐shock fracture behavior of yttria‐doped tetragonal zirconia polycrystals (Y‐TZP) of various grain sizes was evaluated by the quenching method using water as the quenching solvent. The tetragonal‐to‐monoclinic phase transformation behavior of Y‐TZP around cracks introduced by thermal stress was investigated by using Raman microprobe spectroscopy. The critical quenching temperature difference (Δ T c ) of Y‐TZP ceramics increased from 250° to 425°C with increasing grain size of zirconia from 0.4 to 3.0 μm, while the fracture strength decreased from 900 to 680 MPa. The improvement of Δ T c of Y‐TZP with increasing grain size of zirconia corresponded with the quantity of tetragonal‐to‐monoclinic phase transformation around cracks introduced by thermal stress.