Thermal Expansion of Alkaline-Earth-Metal Disilicides AeSi2 (Ae= Ca, Sr, and Ba)

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The thermal expansion of alkaline-earth-metal disilicides AeSi2 (Ae= Ca, Sr, and Ba) has been investigated at temperatures ranging from room temperature to 873 K using powder X-ray diffractometry. The coefficients of linear thermal expansion, αi's, of AeSi2 range from 9 ×10-6 to 18 ×10-6 K-1, which are larger than those of Si (2.6 ×10-6 K-1 at 298 K) and group 4–7 transition-metal disilicides [(6–11) ×10-6 K-1 at 298 K]. The coefficients of volume thermal expansion, αV, range from 3.2 ×10-5 to 4.8 ×10-5 K-1 in AeSi2. The αV becomes larger in the order of CaSi2, SrSi2, and BaSi2. This order of magnitude of αV is related to the order of magnitude of bulk modulus B0 using Grüneisen's rule. The residual stresses in AeSi2 film are discussed using the obtained αi.