Effect of alignment of large grains on the thermal conductivity of self-reinforced beta-silicon nitride

Thermal conductivity of sintered silicon nitride has been improved by the alignment of large beta-Si3N4 grains, Beta-Si3N4 containing 0.5 mol% Y2O3 and 0.5 mol% Nd2O3 was seeded with rodlike beta-Si3N4 grains and tape-cast to align the seed grains. In-situ composite microstructure of the aligned large grains in smaller matrix grains was developed by the grain growth of seed grains during gas-pressure sintering at 2200 degrees C for 4 h. Room-temperature thermal conductivity was anisotropic: 137 W . m(-1) . K-1 in the direction of tape-easting, 97 W . m(-1) . K-1 of seet width, and 12 W . m(-1) . K-1 in the direction of seet stack. The thermal conductivity in the direction parallel to the tape-casting direction was high because of the aligned large grains.