Vaporization thermodynamics of MgB 2 and MgB 4

The vaporization behavior of MgB2 and MgB4 under thermodynamic conditions has been studied by the Knudsen effusion-mass spectrometry technique. In the temperature range explored ~883– 1154 K!, magnesium borides are observed to decompose by loss of gaseous Mg only. The equilibrium pressures of Mg(g) have been measured during high-temperature decompositions involving MgB2 /MgB4 and MgB4 /MgB7 two-phase mixtures and the corresponding standard reaction enthalpies were determined. The decomposition temperatures for MgB2 and MgB4 were also inferred by the relevant Van’t Hoff plots.