β-サイアロンーSiC及びSi_3N_4-SiC加圧焼結体の熱膨張係数 Thermal Expansion Coefficient of Hot-Pressed β-sialon-SiC and Si_3N_4-SiC Composites

The powders of a-Si_3N_4, a-Al_2O_3 and ain were mixed to fabricate β-sialon (formula Si_<6-z>Al_zO_zN_<8-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 a-Si_3N_4, 5 wt% Y_2O_3, 2wt% a-Al_2O_3 and 50 wt% SiC was hot-pressed under the same conditions to get a Si_3N_4-50 wt% SiC composite material. Thermal expansion data of the sintered material was measured from 25 to 1000 ℃ 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 30 wt%. (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 Si_3N_4-50% SiC composite was 3.18X10^<-6>/ ℃. This value was a little higher than Si_3N_4 sintered material but lower than that of SiC sintered material.