Additive-free low temperature sintering of amorphous SiBC powders derived from boron-modified polycarbosilanes: toward the design of SiC with tunable mechanical, electrical and thermal properties

Additive-free SiC ceramics are prepared from polymer-derived powders with Si, C and B elements homogeneously distributed on the atomic level by rapid hot-pressing at 1750 °C and 1800 °C under argon and a load of 50 MPa. As-sintered samples display a Vickers hardness in the range of 9.6 ± 0.5 GPa–17.3 ± 1.9 GPa and an elastic modulus varying from 137 ± 3.4 GPa to 239 ± 6 GPa, both depending on the sample phase composition, crystallinity and porosity. Accordingly, the electrical conductivity changes from 340 to 3900 S/m whereas the thermal conductivity varies from 17.7 to 45.1 W/m⋅K as a function of these characteristics. Thus, we demonstrated that a polycarbosilane containing 0.7 wt.% of boron could produce boron-doped SiC powders that demonstrate tailored sinterability at temperatures as low as 1750 °C to form nearly dense SiC ceramics with adjusted hardness, Young’s modulus, electrical and thermal conductivities.