Effects of M2O3–Y2O3 (M = Sc and Al) additives on electrical conductivity of hot-pressed SiC ceramics

Abstract

Highly densified silicon carbide ceramics were fabricated by hot-pressing β-SiC powders with Sc2O3–Y2O3 and Al2O3–Y2O3 additives. The Sc2O3 and Al2O3 contents of the additives were varied while maintaining a constant Y2O3 content. For the same Y2O3 content (0.849 wt%), the electrical conductivity (σ) of the ceramics decreased to 2.3 × 102, 4.5 × 101, and 5.3 Ω-1 cm−1 with an increase in the Sc2O3 content to 0.259, 0.519, and 1.038 wt%, respectively. Similarly in the case of Al doping, the σ of the ceramics decreased to 1.2, 7.9 × 10−1, and 1.2 × 10−1 Ω−1 cm−1 with an increase in the Al2O3 content to 0.219, 0.437, and 0.874 wt%, respectively, at a fixed Y2O3 content of 0.967 wt%. This decrease in σ can be primarily attributed to the increase in the concentration of the deep acceptors generated by Sc or Al doping in the SiC lattice. The ScSi and AlSi acceptors compensated the NC donors, leading to a decrease in the carrier density of the ceramics. The lower σ of the Al-doped specimens than that of the Sc-doped ones can be attributed to their lower carrier mobility.