Fracture Behavior of High Thermal Conductive Aluminum Nitride

Three kinds of polycrystalline A1N (sample A : 150Wm−1K−1, sample B : 170Wm−1K−1, sample C : 200Wm−1K−1) for which the sintering aid is Yttrium based were used in this study. The fracture toughness of sample A was 3.3MPa m1/2, sample B was 2.8 MPa m1/2, and sample C was 3.1 MPa m1/2. It was shown that the higher the strength of sample, the higher its fracture toughness. The fracture toughnesses of grain and grain boundary were evaluated by substituting the experimental results for the theory on the fracture toughness and the fraction of transgranular fracture. As a result, it was clarified that the reinforcement of grain boundary and grain was achieved in sample A and C, respectively.