Yb_2O_3, Al_20_3, SiO_2を助剤とするSi_3N_4セラミックスの酸化挙動

概要

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Effect of the composition of sintering aids on the oxidation behavior of Si_3N_4 ceramics with Yb_2O_3, Al_2O_3 and SiO_2 additives has been studied at a temperature range from 1210 to 1300℃. The weight gain due to oxidation was affected by the composition of sintering aids and tended to decrease with increasing SiO_2/Yb_2O_3 ratio. In Si_3N_4 ceramics with SiO_2/Yb_2O_3 ratio smaller than about 0.2, the enrichment region of Yb and the depletion region of Yb were formed. The oxidation rate was considered to be affected by the rate of outward diffusion of Yb^<3+> ions. In Si_3N_4 ceramics with SiO_2/Yb_2O_3 ratio larger than about 0.2, the weight loss due to active oxidation was observed. Reason for the formation of depletion region of Yb and the effect of crystallization of grain boundary glass phase on the oxidation kinetics were discussed.
1998-01-01