High temperature phase equilibrium of SiC-based ceramic systems: SiC–Si₃N₄–R₂O₃ (R = Gd, Y) systems

Abstract

The phase relations of the ternary systems SiC–Si₃N₄–R₂O₃ (R = Gd and Y) have been investigated by XRD phase analyses of the hot-pressed samples from SiC, Si₃N₄, and R₂O₃ powders. Their subsolidus phase diagrams were presented. In situ SiO₂ impurity in the powders always led to form some oxygen-richer rare-earth siliconoxynitrides and extend the ternary systems to the quaternary systems of SiC–Si₃N₄–SiO₂–R₂O₃ (R = Gd, Y). Within these systems all rare-earth siliconoxynitrides coexist with SiC. The phase diagrams of the quaternary systems of SiC–Si₃N₄–SiO₂–R₂O₃ (R = Gd, Y) were established, in which the subsolidus diagram of Si₃N₄–SiO₂–Gd₂O₃ system was first reported.