Thermal conductivity of silicon carbide densified with rare-earth oxide additives

In order to fabricate SiC ceramics of high thermal conductivity, a submicrometer-size beta-SiC powder doped with various amounts of combinations of Y2O3 and La2O3 as sintering additives was hot-pressed at 2000 degreesC under 40 MPa for 2 h in Ar, and some hot-pressed specimens were subsequently annealed at 1900 degreesC for 4 h in Ar. The phase compositions and microstructures of the hot-pressed and the annealed SiC ceramics were characterized, and their thermal conductivities were measured by a laser-flash technique. By adding 1 mol% or more additives, full densification was achieved and the materials had thermal conductivities in excess of 166 W/(m K). The thermal conductivities further improved to over 200 W/(m K) after annealing. An explanation on the correlation between thermal conductivity, phase composition, and microstructure was proposed.