Evaluation of thermal conductivity of grains and fillers by using thermoreflectance technique—Si₃N₄, AlN, SiC—

Abstract

In order to clarify thermal conductivity mechanism of ceramics and composites, their local thermal information is very significant. Present work reviewed thermal characterization of non-oxide ceramics at the micrometer scale, and concentrated especially the conductivity of individual grain by a thermal microscope, using thermoreflectance technique and periodic heating. Strong thermal anisotropy was found into very large β-Si₃N₄ grain for developed ceramic. Furthermore, non-homogenous distribution of the conductivity of AlN and SiC ceramics was quantitatively demonstrated in term of thermal conductivity map. Based on the results, the author also discussed high conductivity of AlN and SiC ceramics fabricated with high-purity powders and effective sintering aids, and Si₃N₄ ceramic involving elongated grains with highly orientation.