Porous γ-(Y1-xHox)2Si2O7 thermal insulator with excellent high-temperature strength retention and very low thermal conductivity

High-temperature thermal insulation materials challenge extensive candidates with good mechanical, thermal and chemical reliability at high temperatures. Recently, porous γ-Y2Si2O7 was indicated a promising thermal insulator in harsh environment; however, its strength at 1300 °C reduced to 34% of that at room temperature. In this work, we significantly improved its high-temperature strength by doping Ho. Highly porous γ-(Y1-xHox)2Si2O7 solid solution was fabricated by in-situ foam-gelcasting method. Especially, porous γ-(Y2/3Ho1/3)2Si2O7 demonstrated the optimal high-temperature strength, for instance 65% retention at 1300 °C, as well as high compressive strength (13.9 MPa) and low thermal conductivity (0.186 W/(m K)) at room temperature, at the porosity of 79.3%. Interestingly, porous solid solution sample displayed obviously lower thermal conductivity than the two end pure-phase porous materials. Porous γ-(Y1-xHox)2Si2O7 solid solution is clearly highlighted as a promising high-temperature thermal insulator with outstanding high-temperature strength retention and optimal low thermal conductivity.