Study on the mechanical and low‐temperature degradation properties of 3Y‐TZP doped with nano‐MgO by microwave sintering

Abstract The effects of nano‐MgO content on the microstructure, phase composition, mechanical properties of 3 mol% yttria‐stabilized tetragonal zirconia polycrystal ceramics were studied by microwave sintering at 1300°C–1500°C for 15–120 min. The low‐temperature degradation resistance of the samples was evaluated by hydrothermal experiments. Samples direct microwave sintered at 1500°C for 1 h attained a relative density between 95.5% and 98.2%, with an average grain size of 0.32–0.48 µm, the phase composition was identified as tetragonal ZrO ₂ , with a bending strength of up to 822.07 MPa and a microhardness of 1784.22 HV, with the average friction coefficient ranging from 0.132 to 0.432. Hybrid microwave sintering at 1500°C with 0.8 wt% MgO attained a relative density (94.1–95.4%) and grain size (0.25–0.29 µm) with holding time increases from 15 to 45 min. After hydrothermal treatment at 134°C/0.2 MPa for 60 h, the monoclinic phase content of the samples by direct microwave sintering held at 1500°C for 1 h decreased from 41.43 vol% to 17.85 vol% with the increase in the content of nano‐MgO, indicating that microwave sintering combined with nano‐MgO significantly inhibits the low‐temperature degradation of zirconia composite ceramics.