起電力法によるMo₂BおよびMo₃Siの標準生成自由エネルギーの測定

抄録

In order to obtain the thermodynamic properties of Mo₂B and Mo₃Si, emf measurements of the cells with yttria-stabilized zirconia and calcia-stabilized zirconia as the electrolyte, ⟨Mo⟩ Mo, Mo₂B, B₂O₃ |YSZ| air ⟨Pt⟩ and ⟨Mo⟩ Mo, Mo₃Si, SiO₂ |CSZ| Cr, Cr₂O₃ ⟨Mo⟩, were carried out. The standard free energy of formation of Mo₂B, ΔG°_Mo2B calculated from the emf values was expressed as ΔG°_Mo2B=−112730+6.213T±1070 J/mol (1050–1400 K). The result was compared with those of other investigators. Values of the standard free energy of formation of Mo₃Si, ΔG°_Mo3Si, calculated from the emf values, were almost independent of the temperature in the range from about 1300 to 1400 K, and gave a mean value of −87700±1700 J/mol. The standard entropy of formation, ΔS°_Mo3Si, could not be determined quantitatively, though it was most probable that it had a value close to zero.