Fracture toughness enhancement of yttria-stabilized tetragonal zirconia polycrystalline ceramics through magnesia-partially stabilized zirconia addition

In this work, for the first time, we report a novel method on the fracture toughness enhancement of 3 mol % yttria-stabilized tetragonal zirconia polycrystalline (3Y-TZP) ceramics through the incorporation of 8 mol % magnesia-partially stabilized zirconia (8 Mg-PSZ) powders having high fracture toughness. Highly densified composites (x3Y-TZP/y8Mg-PSZ; where x and y vary between 0.25 and 0.75 wt. %) were obtained with a relative density over 99% by pressureless sintering. Relative density, Vickers hardness (HV) and indentation fracture toughness (K-Ic) were significantly improved by sintering temperature and dwell-time increment. Specifically, HV and K-Ic values of 0.5(3Y-TZP)/0.5(8 Mg-PSZ) composite sintered at 1500 degrees C-2h were increased by 7% and 30%, respectively, compared to that of 3Y-TZP. Sintered bodies consisted of c-ZrO2, t-ZrO2 and m-ZrO2 phases without any new phase formation. m-ZrO2/c-ZrO2+t-ZrO2 volumetric phase ratios changed with the increase of sintering temperature and time. Stress-induced t-ZrO2/m-ZrO2 -> m-ZrO2 phase transformation within c-ZrO2 grains in 8 Mg-PSZ was the main mechanism for toughness enhancement. Energy absorbing mechanisms, e.g., crack-bridging, crack-deflection and crack branching were also found to contribute the blunting of cracks. It is thought that our approach presented herein can be considered not only fracture toughness enhancement but also other properties in various materials for functional and structural purposes. (C) 2020 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.