Redox interaction in redox pair-doped alkali borosilicate melts

The redox interaction behaviors of two redox pairs (Fe+Ce and Fe+Sn) including a single Fe were investigated in alkali alumino-borosilicate melts. The equilibrium states of the melts at a constant temperature, as well as their oxygen equilibrium pressures was determined by potentiometry. The same melts were subjected to voltammetry in the same equilibrium state to examine the Fe redox potential. The interactions between the Fe and Ce or Sn, as determined by the Fe redox ratio based on real oxygen equilibrium pressures, were checked thermodynamically and explicitly manifested by the standard free energy. By comparison of the foregoing results for the melts with the Fe²⁺ absorbance behavior at Vis-NiR spectra for the glasses, it was recognized that the redox interaction in the glass and melt state showed the same tendencies, supporting the derivation of the interaction from the melt state. Additionally, a comparison of the present melts with the results of a previous study on soda lime silicate melts was briefly discussed in terms of the redox interactions in the melt or glass state and the time required to reach the equilibrium state.