Using transmission electron microscopy, we studied aluminum-containing intergranular phases and secondary-phase particles at triple-junctions in SiC (hot-pressed with aluminum, boron, and carbon additions). This study of statistical high-resolution electron microscopy of intergranular films indicated that a large fraction of the vitreous intergranular films (in the as-hot-pressed SiC) crystallized during post-annealing in argon above 1000 °C. However, brief heating to 1900 °C indeed re-melted 25% of the crystallized intergranular films. The structural transitions were reflected in the statistical width distributions of the amorphous grain-boundary layers. At triple-junctions, Al2O3, Al2OC-SiC solid solution, and mullite phases were newly identified. These phases, together with others reported before, are represented in a quaternary phase diagram for 1900 °C. It is proposed that a SiC-Al2OC liquid domain should be included in this phase diagram.

In the title of this paper (and also in several places in the text), the chemical notation for the orthorhombic semiconducting iron disilicide is given incorrectly. In the whole paper, the chemical formula “β-FeSi2.5” should be replaced by the formula “β-FeSi2”.