Theoretical and experimental investigation of chemical vapor deposition of yttrium silicate

Based on the minimum Gibbs free energy principle, thermodynamic calculations of the Y₂O₃–CH₃SiCl₃–CO₂–H₂-Ar system are carried out using FactSage software. Moreover, the influences of deposition temperature, total pressure, the H₂ dilution ratio, and the molar ratio of reactants on thermodynamic phase diagrams and product yield diagrams of the Y₂O₃–CH₃SiCl₃–CO₂–H₂-Ar system have been systematically investigated. Subsequently, based on the calculation results, the X1-Y₂SiO₅ and β-Y₂Si₂O₇ phases are successfully deposited at a lower deposition temperature of 1100 °C, system pressure of 2 kPa, CH₃SiCl₃ flow rate of 39 mL/min, H₂ dilution ratio of 9, and n(CO₂)/n(H₂) ratio of 3:10. In addition, NMR results revealed the molecular structure of the as-deposited yttrium silicate coating, and scanning electron microscopy, which was used for morphological analysis, confirmed the dispersion of yttrium silicate particles in the SiC layer.