Microstructural control of b-silicon nitride ceramics to improve thermal conductivity

An advanced silicon nitride material with high isotropic thermal conductivity (149 W m-1 K-1) has been developed. This high thermal conductivity was achieved with a process that combines high-quality seed crystals with a suitable additive system to promote grain growth. In this process, the addition of β-Si3N4 seed crystals was found to be effective in improving thermal conductivity due to their low defect and impurity concentrations. The seed crystals seem to work as nuclei for controlling grain growth during the sintering process. Controlling the growth of elongated grains so that they do not interact with each other seems important for suppressing the generation of new defects inside the grains.