Low-temperature degradation behaviour of microwave sintered CuO-doped Y-TZP ceramics

Abstract

The low-temperature degradation (LTD) behaviour of undoped and 0.2 % copper oxide-doped 3 mol% yttria-tetragonal zirconia polycrystal (Y-TZP) via microwave (MWV) sintering were studied in this work. The MWV-sintered samples were heated at temperatures varying from 1100 to 1400 °C, with a heating rate of 30 °C per min and holding time of 5 min. These samples were then assessed and compared with the conventional (CV) sintered samples that were executed at the ramp rate of 10 °C per min. The MWV and CV-sintered Y-TZPs were aged in an autoclave vessel and kept in an oven at 180 °C/10 bar up at different intervals, up to 200 h. The results show no substantial difference in the microstructure or grain size between MWV and CV-sintered samples at above 1250 °C. In addition, there was no monoclinic phase detected from the X-ray diffraction (XRD) for both undoped and doped Y-TZPs after ageing for 200 h, regardless of sintering methods, with sintering temperature up to 1400 °C. It was revealed that Y-TZPs with a grain size smaller than 0.28 μm were resistant to hydrothermal ageing. The study also indicated that the beneficial effect of microwave diminished when samples were sintered at elevated temperatures.