Effect of gadolinia on phase structure and thermal conductivity of ZrO 2–4.5 mol%Y 2O 3 ceramics

Abstract

This paper deals with the effect of gadolinia on the phase structure and thermal conductivity of ZrO 2–4.5 mol%Y 2O 3 (YSZ) ceramics for thermal barrier coatings. The YSZ–Gd 2O 3 ceramics were synthesized by solid state reaction at 1500 °C for 2 h in air. The relative density, structure of different YSZ–Gd 2O 3 ceramics and thermal diffusivity in a temperature range of room temperature to 1200 °C were investigated by the Archimedes method, X-ray diffraction and laser-flash method. The ZrO 2–4.5 mol%Y 2O 3 (YSZ) ceramics consist of tetragonal, cubic and a small amount of monoclinic phase, and the YSZ–1.5 mol%Gd 2O 3 ceramics consist of both tetragonal and cubic phases. However, the YSZ–3.0 mol%Gd 2O 3, YSZ–4.5 mol%Gd 2O 3 and YSZ–6.0 mol%Gd 2O 3 ceramics only exhibit a cubic structure. The thermal conductivity of YSZ–Gd 2O 3 ceramics decreases with the increase of gadolinia content under identical temperature conditions. The thermal conductivities of the YSZ and YSZ–1.5 mol%Gd 2O 3 ceramics first decrease gradually with the increase of temperature below 800 °C and then increase slightly above 800 °C. The thermal conductivities of the YSZ–3.0 mol%Gd 2O 3, YSZ–4.5 mol%Gd 2O 3 and YSZ–6.0 mol%Gd 2O 3 ceramics are almost constants from room temperature to 1200 °C.