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 plot

The gaseous molecule CrPO, has been investigated in the course of a high-temperature massspectrometric Knudsen-cell study of the vapours over an europium-chromium-phosphorus-oxygen system. From the enthalpy of the equilibrium reaction CrPO,(g) = CrO(g) + PO(g) and appropriate ancillary data, the atomization energy of this molecule has been determined. In addition, the dissociation energy of CrO(g) has been obtained through the study of the gaseous exchange reactions W03(g) + Cr(g) = W02(g) + C r a g ) EuO(g) and and compared with previous results. 436.2 f 8.9 kJ mol-'. was derived as: L\H&[CrPO,(g)] = 217.6* 13.0 kJ mol-'. The dissociation energies obtained are: (CrP02) = 1438.4* 12.2 kJ mol-', and D F ( C r 0 ) =The appearance potential of CrPO,(g) was determined to be 8.0 f 0.5 eV, and the heat of formation

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The gaseous molecule EuTiO3 has been investigated in a high temperature mass spectrometric study of vapors over the europium–titanium–oxygen system. From the enthalpy of reaction: EuTiO3(g)=EuO(g)+TiO2(g) and proper ancillary data, the atomization energy of this molecule has been determined. In addition, from the study of the gaseous exchange reaction: TiO2(g)+Eu(g)=TiO(g)+EuO(g) the dissociation energy of TiO2(g) has been derived and compared with previous results. The dissociation energies proposed are: D○0,at(EuTiO3) =2278±28 kJ mol−1 and D○0,at(TiO2) =1260±12 kJ mol−1.