Effect of texture on the thermal conductivity and mechanical properties of silicon nitride ceramic

In this study investigated the texture, microstructure, and mechanical behavior of silicon nitride (Si3N4) ceramics were investigated using various techniques, including the orientation distribution function, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The orientation distribution of c-axis of the β-Si3N4 phase derived from the hot-press sintering method, where the considerable orientation arrangement of grains was perpendicular (SPE sample) and parallel (SPA sample) to the hot-pressed direction. XRD analysis showed that the SPA sample had stronger {0001}<10-10> and {0001}<2-1-10> textures than those of the SPE sample. For these reasons, the SPE sample exhibited a lower thermal conductivity of 54 W (m K)−1 than that of the SPA sample (91 W (m K)−1). The mechanical behavior of the Si3N4 ceramics was affected by the orientation arrangement of the grains. Analysis of the cracks on the surface of the Si3N4 ceramics at different indentation angles (0°, 22.5°, 45°, and 67.5°), revealed a rising tendency of fracture toughness in the Si3N4 ceramics, with values of 3.6 MPa m1/2, 4.1 MPa m1/2, 5.5 MPa m1/2 and 6.1 MPa m1/2, respectively. These results were attributed to the texture and close-packed hexagonal structure.