Sintering behavior of tetragonal zirconia ceramic stabilized with yttria and rare earth oxide (YRE) mixtures

The sintering behavior of YRE-ZrO sub 2 powder observed in dilatometric experiments is shown in this work. The powder analyzed was composed by ZrO2 and 6 wt% of YRE oxides mixture, which were added to stabilize the zirconia tetragonal phase. The powder mixtures obtained from controlled zirconium chloride and yttrium and rare earth chloride coprecipitation were calcined at 400 deg C. Isostatic pressing at 400 MPa compacted the powder and the sintering was realized at constant heating rate of 10 deg C /min up to 1600 deg C. At this temperature it was realized an isothermal treatment during 1 hour. The results showed three different stages of sintering during heating, being the two initials stages exhibiting a shrinkage behavior, similar to the majority of the ceramic systems. In the third stage, above 1240 deg C, it was observed a small dilation, which suggests the tetragonal to monoclinic phase transformation in zirconia ceramic. Samples also were conventionally sintered at temperature range between 1200 to 1600 deg C. The X-ray diffraction results and SEM observations were carried out to characterize both the powder mixture and the microstructures of the ceramic bodies. These results were correlated and discussed.