Glass Formation in the System SiO2–PbO Containing Transition-Metal Oxides

Glass-forming regions, valence states, and viscosities in SiO₂–PbO systems containing various transition-metal oxides as a third component were investigated. The glasses were prepared by melting in an open atmosphere. The glass-forming regions ranged as follows: MnO≡ZnO > FeO_1.5>NiO. The ratios Fe²⁺/(Fe²⁺+ Fe³⁺) and Mn³⁺/ (Mn³⁺+ Mn²⁺) in the glasses were determined by chemical analysis. The Fe²⁺/ (Fe²⁺+ Fe³⁺) ratio in SiO₂–PbO–FeO_1.5 glasses ranged from 0.016 to 0.050. The Mn³⁺/ (Mn³⁺+ Mn²⁺) ratio in SiO₂–PbO–MnO glasses ranged from 0.056 to 0.30. The fraction of manganese (III) ions in the glasses varies considerably with the glass composition. The effects of transitionmetal oxides on the viscosity are discussed.