High thermal conductivity in pressureless densified SiC ceramics with ultra-low contents of additives derived from novel boron–carbon sources

In order to attain high thermal conductivity , SiC was doped with ultra-low amounts of B and C as sintering additives using boric acid together with d -fructose as boron–carbon sources. The contents of in situ generated B and C were both tailored as low as 0.4   wt.%, which can significantly reduce the impurities induced phonon scattering effect. The SiC ceramics were pressureless densified at 2150   °C for 1   h, and some samples experienced subsequent annealing at 1950   °C for 4   h. High thermal conductivities of 180.94   W/(m   K) for the as-sintered SiC ceramics and 192.17   W/(m   K) for the annealed specimens at room temperature were achieved. The reasons for the high thermal conductivity in the polycrystalline SiC ceramics were specified, based on the close correlation with microstructure.