Thermal Expansion of the Hexagonal (6H) Polytype of Silicon Carbide

Abstract

The thermal expansion of the hexagonal (6H) polytype of α‐SiC was measured from 20° to 1000°C by the X‐ray diffraction technique. The principal axial coefficients of thermal expansion were determined and can be expressed for that temperature range by second‐order polynomials: α11= 3.27 × 10–6+ 3.25 × 10–9T – 1.36 × 10–12T2 (1/°C), and ş33= 3.18 × 10–6+ 2.48 × 10–9T– 8.51 × 10–13T2 (1/°C). The σ11 is larger than α33 over the entire temperature range while the thermal expansion anisotropy, the δş value, increases continuously with increasing temperature from about 0.1 × 10–6/°C at room temperature to 0.4 × 10–6/°C at 1000°C. The thermal expansion and thermal expansion anisotropy are compared with previously published results for the (6H) polytype and are discussed relative to the structure.