Critical grain size and fracture toughness of 2 mol.% yttria-stabilized zirconia at ambient and cryogenic temperatures

We report, for the first time, the critical grain sizes of 2 mol.% yttria-stabilized zirconia at various cryogenic temperatures determined by in situ phase examination. The grain size dependence of fracture toughness revealed that the maximum toughness value corresponds to the critical grain size at each temperature. On the basis of nucleation and thermodynamic theories, an established linear relationship between inverse critical grain size and temperature is explained and a basic understanding of grain size dependence of toughness at room temperature is also gained.