The phase transformation behavior of Si3N4 with single Re2O3 (Re = Ce, Nd, Sm, Eu, Gd, Dy, Er, Yb) additive

In this work α-Si3N4 powder was heated at 1600–1800 °C for 1.5 h with single rare earth oxide Re2O3 (Re=Ce, Nd, Sm, Eu, Gd, Dy, Er, Yb) additives, respectively. The transformation ratio of α-Si3N4 to β-Si3N4 was determined by X-ray diffraction (XRD) and the behavior of Si3N4 transformation was investigated. The results showed that the all of the Re2O3 additives could increase obviously the transformation ratio of Si3N4 at 1600 °C or more when the amounts were 1 mol%, and the transformation ratio was nearly achieved to 100% at 1700 °C. While the anomalous change of transformation ratio was found when the amount of Re2O3 additive was 3 mol% and the heat temperature was 1600 °C. In addition, it was found that the transformation ratio of Si3N4 changed periodically with the atomic number of the lanthanide at 1650 °C or less.