Low temperature sintering and elongated grain growth of 6H-SiC powder with AlB₂ and C additives

6H(α)-SiC fine powder was sintered at normal pressure with additives of between 0.67 to 2.7 wt.% of AlB₂ and 2 wt.% of C. The powder could be densified at 1850 °C. This sintering temperature was lower than that for SiC with B and C additives by 150–300 °C. During sintering, 6H-SiC partially transformed into 4H-SiC, and the transformation caused grain to grow and develop a nonspherical shape. The fracture toughness of sintered SiC increased with increases in the amount of AlB₂ additive, the mean grain size, and the mean aspect ratio of grain shape. AlB2 and C additives are believed to have formed an Al₈B₄C₇ compound which melted below 1800 °C and enhanced sintering and grain growth.