Theoretical calculations of the hexagonality influence on the mechanical and thermal properties of SiC polytypes

Silicon carbide is one of the most important semiconductor materials in different science fields because of its ability to appear in different crystalline arrangements, which affects its properties. Therefore, Theoretical calculations based on density functional theory (DFT) that performed with CASTEP code were used to investigate the mechanical and thermal properties of four commonly known silicon carbide polytypes 3C, 2H, 4H, and 6H. The calculations were compared with the available data from the experiments and the other’s theoretical studies. Accordingly, the polytypesim effect on these properties was evaluated. The results showed that the four SiC polytypes satisfy the mechanical stability conditions. In addition, the different stacking sequences of the SiC tetrahedron gave a rise of diversity in the structure parameters, which caused in variation in the configuration nature of the bilayers among those polytypes. This difference affected their mechanical and thermal properties. The calculations showed that the cubic polytype has higher hardness and better toughness followed by 4H polytype. The 6H-SiC appeared to be the most brittle polytype followed by 2H and 4H. In addition, the 6H and 2H polytypes showed a higher stiffness. The high Debye temperature of SiC polytypes referred to a high heat capacity, high chemical bonding, and low expansion coefficient. Generally, an inverse relationship appeared between the thermal properties of SiC polytypes and their hexagonality.