Thermal expansion of semiconducting silicides β-FeSi2 and Mg2Si

• β-FeSi2 has linear thermal expansion coefficients of 10.6–11.8 × 10−6 K−1.
• Anisotropy in the linear thermal expansion of β-FeSi2 is small.
• The linear thermal expansion coefficient of Mg2Si is (11 + 0.0069T) × 10−6 K−1.
• Mg2Si has larger thermal expansion than transition-metal disilicides.
• The thermal expansion coefficients of Mg2Si and Ni are similar.

The thermal expansion of β-FeSi2 and Mg2Si was investigated at high temperatures (ranging from 300 to 1173 K for β-FeSi2 and from 293 to 873 K for Mg2Si) using powder X-ray diffraction. The linear thermal expansion coefficients αL for the three lattice parameters of β-FeSi2 range from 10.6(2) to 11.8(4) × 10−6 K−1, which indicates small anisotropy, which is in contrast to the large anisotropy reported previously. The volumetric thermal expansion coefficient αV for β-FeSi2 is relatively large among the transition-metal disilicides. αL for Mg2Si can be expressed by the linear expression of T: αL = 11(1) × 10−6 + 6.9(2) × 10−9T K−1. αV for Mg2Si is larger than that of the transition-metal disilicides, including β-FeSi2. Based on a comparison of αL among Mg2Si, several metals and silicides, the candidates for electrode materials are discussed. In particular, temperature dependence and value of αL for Ni is close to those for Mg2Si, which suggests that Ni is a good candidate electrode material with respect to thermal expansion.