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Temperature dependence of the bulk modulus of MgB2
There are contradictory data in the literature for the temperature dependencies of the isothermal bulk modulus (KT) of magnesium diboride (MgB2). Recently; the present author has calculated the KT of zircon (ZrSiO4) and titanium diboride (TiB2) above room temperature by using the Anderson-Grüneisen equation, the pressure derivative of the bulk modulus and the thermal expansion coefficients (Özkan H, J Eur Ceram Soc 28, 3091 (2008); Intermetallics 19, 596 (2011)). The results obtained for ZrSiO4 and TiB2 verified the method to be a practical way to predict the bulk moduli of materials at high temperatures. In this study the method was extended to calculate the KT of MgB2 above room temperature. The results show that the bulk moduli of MgB2 decrease with increase of temperature from 150.0 GPa at 300 K to 132.2 GPa at 1000 K leading to the temperature derivatives (∂KT/∂T)P of -0.015 GPa/K near 300 K and -0.028 GPa/K near 1000 K. The present results are in good agreements with the corresponding results from the recent first-principle calculations of the elastic constants.
Keywords: Elastic constants, temperature dependence of bulk modulus, pressure dependence of bulk modulus, Anderson-Grüneisen parameter, first-principle calculations, ceramic superconductors.