Effect of CaF2 on sintering behavior and thermal shock resistance of Y2O3 materials

Y2O3 materials have become a popular candidate for preparing refractory crucibles for ultra-pure high-temperature alloy melting in recent years. However, its difficulty in sintering and poor thermal shock resistance limited its industrial application. The effect of CaF2 on the densification microstructure, mechanical properties, and thermal shock resistance of Y2O3 materials was investigated in this paper. The main purpose of this study was to optimize the amount of CaF2 added in the preparation of Y2O3 materials to improve its thermal shock resistance and get better mechanical properties. The mechanism of the densification process of CaF2-doped Y2O3 materials was analyzed by phase analysis and microstructure. The results showed that successive doping of large Ca2+ ions caused more lattice distortion in the Y2O3 materials, and the diffusion rate of Y3+ was increased, thus enhanced grain boundary diffusion and promoted sintering densification in the Y2O3 materials. Meanwhile, the addition of CaF2 also significantly reduced the apparent porosity and enhanced the mechanical properties of the materials. The improvement of these properties was attributed to the increased relative density of CaF2-doped Y2O3 materials and the high sintering activity of CaF2. In addition, crack deflections effectively improved the thermal shock resistance of the materials. The residual flexural strength ratio of Y2O3 materials doped with 1 wt % CaF2 was increased by 21.2% after thermal shock test compared with undoped specimens.