Effect of SiC addition on the thermal diffusivity of SiAlON ceramics

Despite the fact that thermal conductivity is a crucial parameter for SiAlON ceramics with respect to their suitability in various applications, including high-temperature structural components, wear parts, and cutting tools, studies on SiAlON ceramics reported thus far mainly focus on the improvement of their mechanical properties. In view of the lack of sufficient studies on the thermal conductivity of SiAlON ceramics, this study investigates the improvement in the thermal diffusivity behaviour of SiAlON ceramics by the addition of highly conductive SiC particles. As solid-solution SiAlON ceramics exhibit complex crystal structures typically composed of defects, the phonon scattering increases, subsequently decreasing diffusivity. In particular, the improvement in the thermal diffusivity of both alpha- and beta-SiAlONs was investigated by the addition of 0.25 wt% SiC. In addition, the effect of the SiC particle size on the thermal diffusivity of beta-SiAlON was examined. Using inverse diffusivity data, intrinsic and extrinsic scattering parameters were determined, and compared to intrinsic scattering, extrinsic scattering was a dominant factor. Furthermore, transmission electron microscopy (TEM) images of SiCp-reinforced a and -beta-SiAlON ceramics were recorded to examine the SiC particle distribution.