Relation between synthesis process, microstructure and corrosion resistance of two yttrium silicates

Silicon-based ceramics are among the main candidates for high temperature structural components in aeronautic applications. One key drawback of silicon-based ceramics for these applications is the volatilization of the protective silica scale, in moisture and the resulting ceramic recession. Therefore, the further use of these ceramics components depends on the development of external protection against water vapour attack. Some of the most promising materials seem to be rare earth silicates. Based on much richer data in the bibliography, the purpose of this work is to investigate the influence of two yttrium silicates elaboration processes on both the capability to crystallize and the corrosion resistance in an oxidative moist atmosphere at high temperature. Taking into account the material's morphology, composition and degree of crystallization, the composition (Y(2)SiO(5) or Y(2)Si(2)O(7)) and the preferable synthesis process are discussed.