Abstract
The redox behavior of chromium ions in alkali and mixed alkali borate melts was studied by cyclic and differential pulse voltammetries. Half wave potentials for reduction of Cr6+ to Cr3+ were determined in each melt. The half wave potentials shifted progressively to the negative side when alkali ions changed from lithium to sodium, potassium, rubidium and cesium in accordance with the order of the basicity of the melts. The half wave potential of the mixed lithium and cesium melts was more negative than that expected from the mean value of the corresponding potential values of lithium borate and cesium borate melts. This is due to the formation of excess non-bridging oxygens, as suggested by NMR investigation of the mixed alkali glasses.
