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.