Abstract: SiC ceramics were prepared by pressureless sintering with Al, B and C as sintering aids. The effects of the mol ratio of Al and B, the sintering temperature and sintering time
on the relative density and bending strength of the samples were studied. The fracture surface structure and the grain shape of the samples were displayed
by SEM photographs. The experimental result shows that the most appropriate sintering time is 1h, and the relative density of the samples reaches to 90% when the sintering
temperature is above 1850℃. It also shows that the samples have the best prformance when the mol ratio of Al and B is between 3/1 and 4/1. The XRD pattern
shows Al₈B₄C₇ is in existence, which indicates that Al₈B₄C₇ is produced during sintering, so that the sintering mechanism is liquid-phase sintering.

Key words: silicon carbide, Al₈B₄C₇ liquid-phase sintering