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 deg. 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 deg. 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 deg. C