FIGURE 11 Relationships between the thermal conductivities and bending strengths of the AlN ceramics and the O content of the AlN powders
The densities of the AlN ceramics, named S1-S5, corresponding to the P1-P5 AlN powders, respectively, are approximately equal (about 3.3 g/cm3), but the thermal conductivities and bending strengths of them are significantly different. As shown in Figure 11, as the O content of the AlN powder decreased, the thermal conductivities of the AlN ceramics monotonously increase. When the O content of the AlN powder is less than 1.2 wt%, the thermal conductivities of the AlN ceramics increase more dramatically. On the contrary, the bending strengths of the AlN ceramics keep almost constant, as the O content of the AlN powder decreased from 1.46 wt% to 1.2 wt%. And then, they drop accelerately, as the O content of the AlN powder decreased from 1.2 wt% to 0.84 wt%. Definitely, the properties of the AlN ceramics are very sensitive to the O content of the AlN powders.