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Vapor Pressure and Thermal Stability of MgB2 at 0.1 mPa Total Pressure

Published

Author(s)

Lawrence P. Cook, R Klein, Winnie Wong-Ng

Abstract

The vapor pressure of Mg(g) over MgB2(cr) for the reaction 2 MgB2(cr) Mg(g)+MgB4(cr) has been measured thermogravimetrically from 900 degrees celsius to 1100 degrees celsius at 0.1 mPa(1 atm) total pressure using a modified Knudsen effusion method and an elemental Mg calibrant. The experimental data are described by p(Mg) = (9.204370E-08)(exp(1.309524E-02)t) where t is temperature in degrees celsius. These data represent dynamic measurements of MgB2 vapor pressure, as opposed to earlier static measurements reported in the literature. In related differential thermal analysis (DTA) experiments, the Mg/MgB2 eutectic temperature was indistinguishable from the melting temperature of elemental Mg, indicating very small solubility of MgB2 in the eutectic liquid. Up to 1100 degrees celsius, we observed no indication of melting in single-phase MgB2. From our data is it possible to estimate the upper temperature stability limit of MgB2 as occurring at 1235 degrees celsius to 1240 degrees celsius at 0.1 mPa total pressure. Our results are compared with literature data on the thermodynamic properties of MgB2 and possible explanations for the lack of agreement are discussed.
Citation
Physica C-Superconductivity and Its Applications

Keywords

magnesium diboride, melting, MgB<sub>2</sub>, thermodynamics, thermogravimetry, vaporization vapor pressure

Citation

Cook, L. , Klein, R. and Wong-Ng, W. (2017), Vapor Pressure and Thermal Stability of MgB<sub>2</sub> at 0.1 mPa Total Pressure, Physica C-Superconductivity and Its Applications (Accessed April 22, 2024)
Created February 19, 2017