Preparation and phase development of yttria-doped ceria coated TZP powder

This paper presents a simple technique for preparation of yttria-doped ceria (YDC) coated tetragonal zirconia polycrystal (3Y-TZP) powder and its phase development upon firing. The coating solution was prepared using yttrium nitrate hexahydrate and cerium nitrate hexahydrate as starting reagents. Thermochemical reactions of the coated powder were studied using TGA and FTIR while phase development upon firing was examined using XRD. Inward diffusion of the coating YDC into the TZP particles was monitored by observing the change of crystal structure and lattice parameter as a function of sintering temperature and time. At sintering temperature of 1300 °C for 1 h, crystal structure of the sample was still tetragonal (t-ZrO₂). Increasing sintering time to 5 h at 1300 °C, diffusion of YDC into TZP particles occurred drastically and the structure was changed to cubic (c-ZrO₂) as indicated by the disappearance of (002)/(200) peak splitting. Increasing sintering temperature to 1400 and 1500 °C, however, resulted in the co-existence of tetragonal and cubic phases as indicated by the appearance of triples around 72.5–74° 2θ and also the decrease of cubic lattice parameter. When the sintering temperature was further increased to 1600 °C, lattice parameter was only slightly changed, suggesting that inward diffusion of YDC reached saturation point around this temperature.