Preparation and characterization of Al2TiO5 ceramics with low thermal conductivity: role of alumina sources

Abstract

Al₂TiO₅ has received widespread attention due to its lower thermal conductivity in materials with a low coefficient of thermal expansion. Therefore, white fused corundum, tabular corundum and micro α-Al₂O₃ were selected as alumina sources to prepare Al₂TiO₅ by in-situ synthesis in this paper. The influence of alumina sources on the phase compositions, microstructure and thermal conductivity of the samples was investigated. The mechanism of the in-situ synthesis of Al₂TiO₅ was discussed in detail. The results showed that increasing the sintering temperature was beneficial for the formation of Al₂TiO₅. Besides, adding white fused corundum or tabular corundum was conducive to the preparation of Al₂TiO₅. The liquid phase formed by a small number of impurities in the raw materials at high temperatures could accelerate the diffusion velocity of Al³⁺ and Ti⁴⁺, which was beneficial to the formation of Al₂TiO₅ and the stability of its structure. The sample with tabular corundum sintered at 1600 °C had the highest content of Al₂TiO₅ about 86 wt%, and the largest average grain size of 35.3 μm. It also showed satisfactory performance, with the bulk density of 2.99 g/cm³ and the compressive strength of 98.5 MPa. Moreover, the thermal conductivity at 900 °C was reduced to 0.96 W/(m·K) compared to the sample without tabular corundum, which could be used to prepare Al₂TiO₅ ceramics with lower thermal conductivity.