Fabrication and Mechanical Properties of Porous Silicon Nitride Ceramics from Low-Purity Powder

Abstract

Porous Si₃N₄ ceramics were fabricated by normal sintering of low-purity Si₃N₄ powder and 5mass%Y₂O₃ as sintering additive. Porous Si₃N₄ ceramics with >40% porosity were obtained at sintering temperatures in the range 1700-1800°C. The microstructural development, pore morphology, and mechanical properties of these porous ceramics were investigated. The strength of the porous Si₃N₄ ceramics was high for samples sintered at 1800°C. The high flexural strength was contributed by fine elongated β-Si₃N₄ grains and some large elongated grain. This paper outlines the use of low purity powder for the economical fabrication of porous Si₃N₄ ceramics.