Experimental Liquidus Studies of the Pb-Fe-Si-O System in Air

Phase equilibria of the Pb-Fe-Si-O system have been investigated at 958-1913 K (685-1640 °C) for oxide liquid in equilibrium with air and solid oxide phases: (a) quartz, tridymite or cristobalite SiO 2 ; (b) hematite Fe 2 O 3 ; (c) spinel Fe 3 O 4+x ; (d) complex lead-iron silicates (melanotekite PFS = PbO·FeO 1.5 ·SiO 2 , barysilite P 9−x F x S 6 = (9 − x)PbO·xFeO 1+y ·6SiO 2 , “P 5 FS” = 5PbO·FeO 1.5 ·SiO 2 , and “P 6 FS” = 6PbO·FeO 1.5 ·SiO 2 ); (e) lead silicates (alamosite PS = PbO·SiO 2 , P 2 S = 2PbO·SiO 2 , P 11 S 3 = 11PbO·3SiO 2 , P 5 S = 5PbO·SiO 2 ); (f) lead ferrites (magnetoplumbite PbO·12FeO 1.5 , plumboferrite PbO·(5 + x)FeO 1.5 , 1:1 lead ferrite PbO·(1 ± x)FeO 1.5 ); and (g) lead oxide (PbO, massicot). High-temperature equilibration on primary phase or inert metal (platinum, gold) substrates, followed by quenching and direct measurement of Pb, Fe and Si concentrations in the phases with the electron probe x-ray microanalysis (EPMA) has been used to accurately characterize the system in equilibrium with air. All results are projected onto the PbO-“FeO 1.5 ”-SiO 2 plane for presentation purposes. The present study is the first systematic characterization of liquidus over a wide range of compositions in this system in equilibrium with air.