Two kinds of liquid-phase sintering additives, La2O3 and Y2O3, were chosen to achieve the low-temperature sintering process. The relative density and shrinkage at sintering temperatures of 1300 degrees C, 1400 degrees C, and 1500 degrees C respectively were estimated. The observation of microstructures by XRD and SEM reveals that the inhomogeneous phases containing different phase compositions were formed during the sintering. The sintering additives are suggested to increase dielectric constant. However, the La2O3 additive shows no prominent effect on the dielectric loss. We suggest that the effect of aluminate second phase and the microimperfections could play an important role on the dielectric properties of sintered AlN ceramics during sintering below 1500 degrees C.
