Effect of alumina addition on the phase evolution and thermal conductivity of ZrO2–NdO1.5 ceramics

The ZrO2–NdO1.5–AlO1.5 ceramics were synthesized by solid-state reaction at 1600 °C for 10 h in air to fabricate dense bulk ceramics. The relative density, structure and thermal diffusivity of different ZrO2–NdO1.5–AlO1.5 ceramics were investigated by the Archimedes method, X-ray diffraction (XRD), scanning electron microscopy (SEM), laser Raman spectroscopy and laser-flash method. The thermal conductivity was calculated from density, specific heat and thermal diffusivity in a temperature range of room temperature to 1400 °C. The Nd2Zr2O7 ceramics doped without alumina only exhibit a pyrochlore-type lattice. The 47.1ZrO2–47.1NdO1.5–5.8AlO1.5 and the 44.2ZrO2–44.2NdO1.5–11.6AlO1.5 ceramics (mol%) consist of both perovskite-like NdAlO3 and pyrochlore structures. However, the 41.3ZrO2–41.3NdO1.5–17.4AlO1.5 ceramics consist of both perovskite-like NdAlO3 and fluorite (F-ZrO2) structures, and the 38.4ZrO2–38.4NdO1.5–23.2AlO1.5 ceramics consist of perovskite-like NdAlO3, F-ZrO2 and hexagonal β-Al2O3-type structures. The thermal conductivities of different ZrO2–NdO1.5–AlO1.5 ceramics increase with the increase of alumina concentration in raw materials under identical temperature conditions. The thermal conductivities of ZrO2–NdO1.5–AlO1.5 ceramics in this investigation were located in the range of 1.50–3.22 W m−1 K−1 from room temperature to 1400 °C.