Investigation on mechanical properties of 6H-SiC crystal

In this work, the mechanical properties, such as Vickers microhardness H-v, fracture toughness K-c, yield strength sigma(v) and brittleness index B-i, of < 0001 > oriented 6H-SiC crystal are systematically evaluated using a microindentation technique under 0.1- 2 kg applied load. It is found the H-v is decreased as the applied load is increased which is mainly attributed to the effect of indenter penetration. The H-v value can be effectively presumed by Kick's law and the Meyer's index n is determined to be 1.73. However, the K-c value is measured nearly a constant (similar to 0.148 MPa.m(1/2)) which reveals the toughness of 6H-SiC(0001)) crystal is much weaker than those of Si-(100) and GaAs(100) crystals. The variation of sigma(v) to the load is similar to that of H-v. The brittleness index B-i also exhibits deceasing tendency as the applied load is added.