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

Published

February 19, 2017

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

Pub Type

Journals

Keywords

magnesium diboride, melting, MgB₂, thermodynamics, thermogravimetry, vaporization vapor pressure

Citation

Cook, L. , Klein, R. and Wong-Ng, W. (2017), Vapor Pressure and Thermal Stability of MgB₂ at 0.1 mPa Total Pressure, Physica C-Superconductivity and Its Applications (Accessed April 25, 2024)