A series of silicon carbide-based ceramics with different sintering additives were liquid-phase sintered to high densities. Yb2O3 in combination with AIN was used as the additive, instead of the commonly used Y2O3-AIN, to improve the refractoriness of the secondary phase. Thermo-chemical decomposition of AIN was sufficiently suppressed with the use of nitrogen overpressure and reasonable weight loss was achieved in the different additive containing SiC ceramics without a reactive powder bed. Use of the heavier rare-earth element modified the liquid phase formed during sintering and reduced the phase transformation controlled grain growth rate, compared with Y2O3 doped materials. It also permitted microstructure tailoring through post-sintering heat treatments in nitrogen. Materials with self-reinforced microstructures, formed as a result of anisotropic grain growth, were obtained. Improved fracture toughness (4.5-5 MPa/m(1/2)) and good flexural strength retention up to 1400° C were also observed.