Microstructures, thermophysical properties and corrosion behaviours of equiatomic five-component rare-earth monosilicates

Abstract

Four equiatomic five-component rare earth monosilicates solid solutions were prepared by spark plasma sintering. Two compositions with larger deviation of ionic radii, (Dy0.2Ho0.2Er0.2Tm0.2Yb0.2)2SiO5 and (Dy0.2Ho0.2Er0.2Y0.2Lu0.2)2SiO5, exhibit single-phase structures and homogenous elemental distributions. Extremely low high-temperature thermal conductivities below 1 Wm−1 K−1 and similar coefficients of thermal expansion with SiC were achieved for both compositions. Further, they both displayed good high-temperature stability and high corrosion resistance in water vapor. When exposed to 1400 °C, 90%RH water vapor, only slight weight losses were observed for both compositions during the initial half hours, after which almost no further weight losses were observed.