Effect of AlN addition on the electrical resistivity of pressureless sintered SiC ceramics with B4C and C

Abstract

AbstractThe effect of 0–12 wt% AlN addition on the electrical resistivity of SiC ceramics pressureless sintered with 0.7 wt% B4C and 2.5 wt% C additives was investigated. The elemental analysis of SiC grains revealed a codoping of Al and N in the SiC lattice with a higher N concentration with 1 wt% AlN addition and a higher Al concentration with 12 wt% AlN addition. The electrical resistivity decreased by four orders of magnitude (1.7 × 105 → 8.3 × 101 Ω cm) with 1 wt% AlN addition due to the increased carrier density (1.7 × 1010 → 2.3 × 1015 cm−3) caused by excess N‐derived donors. However, subsequent AlN addition (4 → 12 wt%) led to an increase (2.9 × 103 → 1.2 × 104 Ω‧cm) in electrical resistivity due to (1) increased Al dopants which act as deep acceptors for trapping N‐derived carriers causing a decrease in carrier density (2.3 × 1015 → 5.9 × 1013 cm−3), (2) the formation of electrically insulating SiC‐AlN solid solution, and (3) the presence of electrically insulating AlN grains at the grain boundaries.