Polymorphism in Silicon Carbide

Abstract

SILICON carbide exists in two distinct crystalline polymorphs, the cubic or β-form, and the hexagonal or α-form^1–3. Although the crystal structure and related physical properties of the two forms of silicon carbide have been extensively investigated, the chemical relationship between the two silicon carbide polymorphs has apparently failed to receive equivalent attention. The problem was attacked by Baumann⁴, who investigated both the chemistry of silicon carbide formation, and the rate of conversion of β-silicon carbide to α-silicon carbide at several temperatures. Baumann observed that although β-silicon carbide began to transform to α-silicon carbide slowly at 2,100° C, the reaction was rapid at 2,300° C.