Phase Relations in the System Lead—Oxygen

Most of the known oxides of lead including the intermediate oxides Pb₁₂O₁₉ and Pb₂O₃ have been prepared under equilibrium conditions. Precise X-ray powder data have been obtained for the intermediate oxide phases. Solid-vapor equilibrium data have been obtained for reactions in the system lead-oxygen over the range 200° to 900° C and 3 to 1400 bars Po₂. Pressure-temperature univariant equilibrium curves are presented for the reactions PbO₂⇋ Pb₁₂O₁₉+ oxygen, Pb₁₂O₁₉⇋ Pb₃O₄+ oxygen, and Pb₃O₄⇋ PbO + oxygen. The enthalpies of reaction are, respectively, 26.8, 34.6, and 33.7 kcal per mole. Eutectic melting between PbO and Pb₃O₄ occurs at 875° C and 124 bars. A stability field for Pb₂O₃ exists above 1000 bars PO₂ at 600° C. Approximate resistivity data are presented.