It has recently been reported that in the Y203-stabilized tetragonal zirconia phase (TZP) system the addition of a small amount of transition-metal oxides (e.g. CuO, MnO and ZnO) which form a liquid or amorphous grain boundary phase significantly enhances superplasticity [1, 2]. In CuO-added 2Y-TZP abrupt changes have been found in the stress exponent and activation energy across the melting te...