Thermal Expansion Coefficient of Hot-Pressed β-sialon-SiC and Si<sub>3</sub>N<sub>4</sub>-SiC Composites

The powders of α-Si3N4, α-Al2O3 and AlN were mixed to fabricate β-sialon (formula Si6-ZAlZOZN8-Z with 4 excess oxygen eq.% over Z=1, 2, 3 and 4). A SiC powder was added to the β-sialon powder mixture and hot pressed to get β-sialon-SiC composites. A powder mixture of α-Si3N4, 5 wt% Y2O3, 2wt% α-Al2O3 and 50 wt% SiC was hot-pressed under the same conditions to get a Si3N4-50 wt% SiC composite material. Thermal expansion data of the sintered material was measured from 25 to 1000°C by dilatometric method.The results are obtained as follows:(1) The thermal expansion coefficient of the β-sialon-SiC composites gradually increased with an increase in SiC addition up to 30wt%.(2) The thermal expansion coefficient of β-sialon-50 wt% SiC composites gradually increased with an increase of Z value.(3) The thermal expansion coefficient of Si3N4-50% SiC composite was 3.18×10-6/°C, This value was a little higher than Si3N4 sintered material but lower than that of SiC sintered material.