Systematic studies of the effects of additives and processing variables on the sintered density and the effect of crystalline forms of starting powders on the microstructure of pressureless sintered silicon carbide are described. Oxide additives were effective for the densification of SiC up to 96% of theoretical density at temperature as low as 185$0^{circ}C$. Use of embedding powder increased the sintered density, up to 98% of theoretical density, by decreasing the weight loss during sintering. Composite type duplex microstructure has been developed due to the $eta$longrightarrow$alpha$ phase transformation of SiC by sintering at 185$0^{circ}C$ and heat treatment at 195$0^{circ}C$ for 1h.