High Thermal Conductivity Non-Oxide Ceramics.

Thermal conductivity is one of significant physical properties of engineering materials. It has been confirmed through the thermal conductivity measurements of natural and synthetic materials, and from theoretical calculations that the theoretical conductivities of diamond, BN, SiC, BeO, BP and AlN are larger than 300W·m-1·K-1 at room temperature, being classed as high thermal conductivity solids. Non-oxide ceramic polycrystals with conductivities close to those of single crystals have been developed through the advances in ceramic processing. In recent years, the thermal conductivity exceeding 150W·m-1·K-1 has been reported for β-Si3N4 ceramics, joining a group of high thermal conductivity solids. The non-oxide ceramics have been progressively used as heat-dissipating substrates for highly integrated circuits and optoelectronics, structural components for producing semi-conductors, engine-related material components and so on. Accordingly, the significance of high thermal conductivity non-oxide ceramics has been highly recognized in many industrial fields. In this review, the test results of thermal conductivity of non-oxide ceramics, such as SiC, AlN and Si3N4, are summarized, and then, the effects of processing and microstructural parameters on their thermal conductivities are discussed. Based on the experimental data, the mechanisms of thermal conduction in non-oxide ceramics are examined. The processing strategy leading to high thermal conductivity non-oxide ceramics is also addressed.