Study on sintering behaviour of ytterbium disilicate and ytterbium monosilicate for environmental barrier coating applications

Yb2Si2O7 (YbDS) and Yb2SiO5 (YbMS) are two promising materials being developed as environmental barrier coatings (EBC) for the protection of Ceramic Matrix Composites (CMC) applied to gas-turbine engines operating in high-temperature corrosive environments. In this work, sintering behaviours of YbDS, YbMS, and YbDS/YbMS composites compacts were investigated. The effect of the thermal ageing at 1350 degrees C on microstructural characteristics as well as crack healing and elastic properties were examined. It was found that YbDS had a lower critical sintering temperature and higher grain growth rate than that of YbMS due to lower activation energy. The sintering behaviour of the YbDS/YbMS composites showed that the addition of YbMS retarded the grain growth rates and contributed to the stabilisation of the elastic properties. In addition to this, composite containing 22 wt %YbMS displayed a crack healing behaviour during high-temperature exposure, which was attributed to the generation of compressive stress, consequently accelerated diffusion in the YbDS matrix.