Ion Migration Study in a Sodium Borate Glass: Proposal of a New Oxide Transport

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Abstract
Electrolysis of the cell was investigated at 50°C, using a modified moving boundary method (in the anode region) based upon sodium and lead concentration profiles (obtained by ion beam ablation) and ultraviolet spectroscopy of the Pb2+ ion. It was found that Na+ ions left the anode region for the cathode but, contrary to related experiments with silicate glasses, there was not an equivalent replacement by the Pb2+ ions generated at the anode. Instead, O2− ions migrated to the anode and most of the Pb2+ ions formed . It is suggested that a “structure‐switching ion transport” mechanism operates, migration of the O2− ions involving an interchange between threefold and fourfold coordination by the boron atoms as the oxygens are handed on from one borate group to the next. The ultraviolet spectrum of the small concentration of Pb2+ ions in the anode region registered a lower basicity than the original glass (optical basicity values 0.49 and 0.60, respectively) but the sites were more basic than for a corresponding borate glass obtained from the melt.

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