3Y-TZP ceramics toughened by Sr2Nb2O7 secondary phase

3 mol% yttria stabilized tetragonal zirconia ceramics (3Y-TZP) were significantly toughened by a Sr2Nb2O7 ferroelectric secondary phase incorporated into the matrix to serve as toughening agent. A high KIC value, 13.0 MPa.m1/2 was achieved in 1 mol% Sr2Nb2O7 composite ceramics, while that of the 3Y-TZP matrix was 6.0 MPa.m1/2. Energy transformation and consumption due to piezoelectric effects and domain wall motion was suggested as an important toughening mechanism along with that of phase transformation toughening. Moreover, it should be emphasized that a high KIC value of 12.0 MPa.m1/2 was achieved in the present composite ceramics even where the transformation toughening mechanism was inactive.