Standard molar Gibbs energy of formation of Pb5Bi8O17 and PbBi12O19 and phase diagram of the Pb–Bi–O system

Equilibrium phase fields of the ternary Pb–Bi–O system were established by long-term equilibration in the temperature range 660–840 K. Using these results, the partial phase diagram of the ternary system has been constructed. The standard molar Gibbs energy of formation of the ternary oxides, 〈Pb5Bi8O17〉 and 〈PbBi12O19〉, was determined by measuring the equilibrium oxygen partial pressures over the relevant phase fields by static manometry in conjunction with a solid oxide electrolyte-based emf cell. Further, the standard molar Gibbs energy of formation of 〈Pb3O4〉 was also measured by the manometric method. The oxide that coexists with the Pb–Bi eutectic alloy (LBE) has been experimentally confirmed as [β-PbO]ss. Using the thermochemical data measured, the compositions of Pb–Bi alloys that coexist with [β-PbO]ss and ternary oxides were derived and reported.