Synthesis of powder and bulk ceramics of a new ternary Na-Si-B compound

Abstract

Na₈B_74.5Si_17.5 was synthesized by heating a mixture of sodium, silicon and amorphous or crystalline boron at 1073−1273 K. The black hexagonal prismatic single crystals were obtained at 1273 K. Na₈B_74.5Si_17.5 bulk ceramics was prepared by heating a compact of boron powder with Na and Si at 1173 K. The bulk ceramics had a density of 1.90 Mg/m³, which was about 77 % of the theoretical density (2.48 Mg/m³). The fracture bending stress of the Na₈B_74.5Si_17.5 bulk was evaluated to be 104 MPa at room temperature.