Sintering of Silicon Carbide Ceramics with Additives Based on the (Y2O3-Al2O3-SiO2) System

Abstract

The sintering behavior of silicon carbide using alumina, silica and yttria as additives was investigated. Powders containing 90 vol. % SiC and 10 vol. % additives (keeping 1Y2O3:1Al2O3 molar ratio) were sintered at 1950°C/1h, in a dilatometer or a graphite resistance furnace. Thermal treatments were also done from 1500°C/1h up to 1800°C/1h, in order to evaluate the formation of transient crystalline secondary phases. The sintered samples were characterized through XRD, SEM and TEM analysis. The results showed that sintering behaviour is clearly related to the additive composition investigated, as demonstrated by linear shrinkages and linear shrinkages rate curves. Temperatures of particle rearrangment, solution-reprecipitation of SiC grains, as well as secondary crystalline phase(s) formation and dissolution could be revealed after dilatometric analysis. These temperatures are in good agreement with XRD results. Microstructural observations through SEM and TEM analysis are also related to the sintering behaviour.