Elastic constants of MoSi₂ and WSi₂ single crystals

Abstract

Single crystals of MoSi₂ and WSi₂ with a body-centred-tetragonal C 1 1_b structure were fabricated using a floating-zone method. The elastic wave velocity was measured for samples with various orientations using a simple pulse echo method at room temperature, and six elastic stiffness constantsc _ij were calculated. The stiffness constants were a little higher for WSi₂ than for MoSi₂.c ₁₁ andc ₃₃ of these compounds were approximately equal toc ₁₁ of tungsten and molybdenum, respectively, althoughc _ij (i ≠j) was a little higher for these compounds than for molybdenum and tungsten. Young's modulus 1/s ₁₁ was the highest in the <0 0 1> direction, and the lowest in the <1 0 0> direction. The shear modulus 1/s ₆₆ was high on the {0 0 1} plane and independent of shear direction. It was generally low on the close-packed {1 1 0} plane and largely dependent on shear direction. The elastic constants for the polycrystalline materials were estimated fromc _ij ands _ij . Poisson's ratiov was 0.15 for MoSi₂ and for WSi₂, and these values were much lower than for ordinary metals and alloys. The Debye temperature θ_D was estimated using the elastic-wave velocity of the polycrystalline materials via the elastic constants such as Young's modulus and shear modulus: it was 759 K for MoSi₂ and 625 K for WSi₂.