Abstract
Room-temperature elastic properties of hexagonal C40 NbSi2 single crystal have been determined using resonant ultrasound spectroscopy (RUS). All five independent elastic stiffness constants cij were obtained: c11 = 380·2, c33 = 468·0, c44 = 145·3, c12 = 75·9 and c13 = 88·3 GPa. The shear modulus c66 in the (0001) plane, 152·2 GPa, is low relative to those of MoSi2 and WSi2. The isotropic elastic constants for polycrystalline material were also calculated. The results show that the bulk modulus K. shear modulus G and Young's modulus E are much higher than those of the constituent elements. The room temperature Poisson's ratio of the compound is 0·18, which is much smaller than those of the constituent elements and most observed materials. The elastic properties of C40 NbSi2 and C11b MoSi2 and WSi2 are compared and the possible influence on the mechanical behaviour is discussed.