Preparation and thermophysical properties of (NdxGd1−x)2Zr2O7 ceramics

Ceramic powders of (Nd x Gd 1− x ) 2 Zr 2 O 7 ( x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) were synthesized by chemical-coprecipitation followed by calcination method, and were then pressureless-sintered at 1,600 °C for 10 h in air. Phase constituents and morphologies of the synthesized powders and sintered ceramics were identified by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A high-temperature dilatometer and a laser-flash method were used to analyze the thermal expansion coefficient and thermal diffusion coefficient of different ceramics from room temperature up to 1,400 °C. Thermal conductivity was calculated from thermal diffusivity, density, and specific heat. (Nd x Gd 1− x ) 2 Zr 2 O 7 (0.1 ≤ x ≤ 1.0) ceramics are with a pyrochlore-type structure; however, pure Gd 2 Zr 2 O 7 exhibits a defective fluorite-type structure. The average linear thermal expansion coefficients of different (Nd x Gd 1− x ) 2 Zr 2 O 7 ceramics decrease with increasing the value of x from 0 to 1.0 in the temperature range of 25–1,400 °C. The thermal conductivities of (Nd x Gd 1− x ) 2 Zr 2 O 7 ceramics are located within the range of 1.33 to 2.04 W m −1 K −1 from room temperature to 1,400 °C.