Electrical properties of SiC ceramics sintered with 0.5 wt% AlN–RE2O3 (RE=Y, Nd, Lu)

Silicon carbide ceramics with 0.5 wt% AlN–RE2O3 (RE=Y, Nd, Lu) additives were prepared by hot-pressing the powder mixtures at 2050 °C for 6 h under an applied pressure of 40 MPa in a nitrogen atmosphere. The effects of additive composition on the sinterability, microstructure, and electrical properties of hot-pressed liquid-phase sintered (LPS)-SiC ceramics were investigated. It was found that all specimens could be sintered to >95% of the theoretical density by adding 5 wt% in situ-synthesized nano-sized SiC and 0.5 wt% AlN–RE2O3 additives. SiC ceramics sintered with AlN–Y2O3 and AlN–Nd2O3 showed low electrical resistivity on the order of 10−2 Ω cm. This low electrical resistivity was attributed to the growth of nitrogen-doped SiC grains and the confinement of non-conducting RE-containing phases in the junction areas. The electrical resistivity of LPS-SiC ceramics sintered with AlN–RE2O3 was dependent on the chemistry of the additive composition.