Low thermal conductivity and anisotropic thermal expansion of ferroelastic (Gd1−xYx)TaO4 ceramics
Chenkai Qu, Lin Chen, Liang Lv, Yuncheng Wang, Xiaolan Ji, Haitao Yun, Chaoqun Su, Jing Feng
Abstract
Abstract In this paper, (Gd 1− x Y x )TaO 4 ceramics had been fabricated by solid-phase synthesis reaction. Each sample was found to crystallize in a monoclinic phase by X-ray diffraction (XRD). The properties of (Gd 1− x Y x )TaO 4 were optimized by adjusting the ratio of Gd/Y. (Gd 1− x Y x )TaO 4 had a low high-temperature thermal conductivity (1.37–2.05 W·m −1 ·K −1 ), which was regulated by lattice imperfections. The phase transition temperature of the (Gd 1− x Y x )TaO 4 ceramics was higher than 1500 °C. Moreover, the linear thermal expansion coefficients (TECs) were 10.5×10 −6 K −1 (1200 °C), which was not inferior to yttria-stabilized zirconia (YSZ) (11×10 −6 K −1 , 1200 °C). (Gd 1− x Y x )TaO 4 had anisotropic thermal expansion. Therefore, controlling preferred orientation could minimize the TEC mismatch when (Gd 1− x Y x )TaO 4 coatings were deposited on different substrates as thermal barrier coatings (TBCs). Based on their excellent properties, it is believed that the (Gd 1− x Y x )TaO 4 ceramics will become the next generation of high-temperature thermal protective coatings.