Tunable properties of (Ho(x)Y(1-x))(2)SiO(5) as damage self-monitoring environmental/thermal barrier coating candidates

RE(2)SiO(5) with low thermal conductivity, compatible thermal expansion coefficients and excellent high-temperature reliability in harsh environments are excellent candidates as advanced environmental/thermal barrier coating materials for high-efficiency gas turbine engines. A series of rare earth silicates (Ho(x)Y(1-x))(2)SiO(5) are designed and their properties are comprehensively investigated in this paper. Through doping Ho into Y(2)SiO(5), the thermal conductivity of Y(2)SiO(5) is significantly decreased and the thermal expansion coefficient is also optimized closer to Si-based ceramics. High-temperature elastic stiffness and bending strength are increased with the enhancing of Ho content. Most important, doping Ho element provides (Ho(x)Y(1-x))(2)SiO(5) with tunable luminescence characteristic. (Ho(x)Y(1-x))(2)SiO(5) exhibit green, to yellow-green, then to orange-red luminescence color with increased Ho concentration. The results show that they can be used as damage self-monitoring environmental/thermal barrier coating materials for Si-based ceramics.