Aluminium oxide (Al2O3)-aluminium nitride (AlN) composites were prepared at 1500-1600 oC by pressureless sintering. The main raw materials used were AlN and Al2O3, and appropriate amounts of TiO2-Y2O3-CaO-La2O3 quaternary sintering aids were added. The effects of different AlN contents and sintering temperatures on the bulk density, bending strength, Rockwell hardness, thermal conductivity, and other properties of Al2O3-based ceramics were studied. The phase composition and microstructure of the samples were analysed with an X-ray diffractometer and scanning electron microscope. Results showed that the Al2O3-AlN composites had excellent overall performance in terms of a flexural strength of 295.7MPa, a Rockwell hardness of 61.5 HRA, and a thermal conductivity of 38.8W/(m·K) (at 25 oC) after pressureless sintering at 1600 oC for 3 h with 10 wt% AlN content. These properties met the requirements of high-power ceramic LED lamp holders. The Al2O3- 10 wt%AlN composites sintered at 1600 oC had a dense microstructure, tight bonding among grains, and few pores, which explained the excellent performance of the samples.

Keywords: AlN, Al2O3 ceramics, Pressureless sintering, Thermal conductivity, Microstructure.