Effects of different types of rare earth oxide additives on the properties of silicon nitride ceramic substrates

Abstract 5 wt% of different types of rare earth oxides (Re2O3, Re = Lu, La, Yb, Y, Nd, Er, Sm, Ce, Dy, Eu, Gd) and 2 wt% MgO as additives were selected in this study based on previous studies on rare earth oxide additive concentrations. The effects of rare earth oxide type on the microstructure, phase composition, thermal conductivity, mechanical properties, and dielectric properties of silicon nitride ceramics were systematically investigated. Samples doped with rare earth oxides with smaller ionic radii (such as Yb2O3, Lu2O3, Er2O3, and Dy2O3) showed higher thermal conductivity. Samples doped with Eu2O3 and Yb2O3 showed fine-grained microstructures due to inhibition of dissolution, diffusion, and re-precipitation of silicon nitride. Silicon nitride ceramics doped with Eu2O3 showed the lowest thermal conductivity and dielectric constant (