Abstract:AlN ceramic powders with the different oxygen contents were prepared by the carbon-thermal reduction method through controlling the carbon removal process, using Al ₂O ₃powders and carbon black as raw materials. The mass fraction of oxygen in high-oxygen AlN powders was 0.9%, and that in low-oxygen AlN powders was 0.6%. The AlN ceramic samples were prepared using these high-oxygen and low-oxygen AlN ceramic powders. The bending strength and thermal conductivity of the AlN ceramics were tested within the range of 77～350 K by the three-point bending method and the 3 ωmethod. The influence of oxygen content on the bending strength and thermal conductivity of AlN ceramics was discussed and compared with those of Al ₂O ₃ceramics and Si ₃N ₄ceramics. The results show that the content of the second phases is relatively high in the high-oxygen AlN ceramic samples, while it is relatively low in the low-oxygen AlN ceramic samples. The second phases inhibit the growth of AlN grains and play a role in fine-grained strengthening. However, the presence of the second phases reduces the free path of phonons and the thermal conductivity. Within the experimental temperature range, the bending strength of high-oxygen AlN ceramic samples is higher than that of low-oxygen AlN ceramic samples, and the thermal conductivity is lower than that of low-oxygen AlN ceramic samples. The room-temperature bending strength of AlN ceramics is slightly higher than that of Al ₂O ₃ceramics, but not as good as that of Si ₃N ₄ceramics. The room-temperature thermal conductivity of AlN ceramics is higher than that of Al ₂O ₃ceramics and Si ₃N ₄ceramics, reaching 200 W·m ⁻¹·K ⁻¹. Meanwhile, the AlN ceramics can maintain high thermal conductivity and relatively high bending strength at low temperatures. Therefore, compared with Al ₂O ₃ceramics and Si ₃N ₄ceramics, the AlN ceramics have a wider range of low-temperature applications.