Use of thallium(I) probe for identifying sites of mobile cations in glass during electrolysis

Abstract

Ion-profile analysis (by ion sputtering) and ultraviolet spectroscopic examination of thin plates (0.5 mm) of sodium borate glass (35 mol% Na₂O), subjected to electrolysis using a thallium-amalgam anode and a platinum cathode, reveal migration of some sodium ions from the anode region and their replacement, at least partially, by thallium ions. The ¹S₀→³P₁ frequency of the Tl⁺ indicates that the sites have much higher than average basicity (optical basicity is 0.66–0.67 compared with the average value for the glass of 0.53), although it is not certain whether these sites are the ones originally accommodating the mobile sodium ions, since the present work provides no proof of direct substitution by the thallium ions. The results contrast with those previously obtained, using lead as anode material, when a structure-switching mechanism resulted in oxide-ion migration and almost total depletion of sodium oxide from the anode region.