A composition and method of fabricating pressureless sintered 70 volume % silicon nitride--30 volume % barium aluminum silicate ceramic composites. The composites are made from 70 volume % silicon nitride, containing varying amounts and size distributions of initial .beta.-silicon nitride, and 30 volume % barium aluminum silicate. The resulting ceramic composites contain microstructures with coarse .beta.-silicon nitride whiskers, as well as narrow distributions of short .beta.-silicon nitride whiskers, surrounded by fine barium aluminum silicate grains. The resulting composites exhibit improved fracture toughness and flexural strength.