Effect of alumina addition on the phase evolution and thermal conductivity of ZrO₂-NdO_1.5 ceramics

The ZrO₂-NdO_1.5-AlO_1.5 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-NdO_1.5-AlO_1.5 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 47.1ZrO₂-47.1NdO_1.5-5.8AlO_1.5 and the 44.2ZrO₂-44.2NdO_1.5-11.6AlO_1.5 ceramics (mol%) consist of both perovskite-like NdAlO₃ and pyrochlore structures. However, the 41.3ZrO₂-41.3NdO_1.5-17.4AlO_1.5 ceramics consist of both perovskite-like NdAlO₃ and fluorite (F-ZrO₂) structures, and the 38.4ZrO₂-38.4NdO_1.5-23.2AlO_1.5 ceramics consist of perovskite-like NdAlO₃, F-ZrO₂ and hexagonal β-Al₂O₃-type structures. The thermal conductivities of different ZrO₂-NdO_1.5-AlO_1.5 ceramics increase with the increase of alumina concentration in raw materials under identical temperature conditions. The thermal conductivities of ZrO₂-NdO_1.5-AlO_1.5 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.