Effects of boron source on properties of pressureless solid-state sintered silicon carbide ceramics

Abstract

The effects of the boron source (B, BN, and B4C) on the thermal, electrical, and mechanical properties of pressureless solid-state sintered SiC ceramics were investigated. A high relative density of 99.9 % was successfully achieved for all ceramic specimens using an appropriate additive composition and ideal sintering conditions. SiC ceramics sintered with B and B4C additives displayed higher electrical and thermal conductivities and higher flexural strength than those sintered with the BN additive at the same relative density. The presence of intrinsically-weak, electrically-insulating BN grains at the junction and grain boundaries increased both the fracture toughness and electrical resistivity, while the flexural strength and thermal conductivity of the ceramics decreased. The electrical resistivity, thermal conductivity, and flexural strength of the SiC ceramics were able to be adjusted with values ranging from 3.2 × 104–1.6 × 106 Ω‧cm, 72.4–147.5 W‧m−1‧K−1, and 386–545 MPa, respectively, depending on the boron source used.