Enhanced electrical resistivity in SiC–BN composites with highly-active BN nanoparticles synthesized via chemical route

Abstract

In order to fabricate SiC–BN composites with enhanced electrical resistivity, boric acid and urea were used as reactants for synthesizing nano-sized BN particles on the surfaces of SiC powders in flowing ammonia atmosphere. The composites containing 10 wt% BN were pressureless densified at 2150°C for 1h with B4C and C as sintering additives. The chemical route was advantageous for obtaining finer BN dispersoids and microstructures of higher homogeneity, which significantly enlarged the SiC/BN interdiffusion area. Consequently, the concentrations of dissolved B and N in SiC grains became more equivalent and the carrier concentration was further decreased through impurity compensation mechanism. The chemically processed composite exhibited a considerably high electrical resistivity (1.03×1012Ωcm), which was ∼15 times higher than that of the composite prepared by conventional powder mixing method. Besides, considerably low dielectric constant (13.88) and loss tangent (0.128) at 1MHz, as well as good thermal conductivity (70.08Wm−1K−1) were also achieved.