Ionic direct current and thermally stimulated depolarization currents in connection with the structure of alkali borate glasses

Abstract

Ionic direct current (DC) and thermally stimulated depolarization currents (TSDC) in alkali borate glasses have been measured by varying K2O and iodine content, aiming to understand behaviors of iodine as well as potassium ions in the borate glass. The DC in the borate glasses increased with increase of K2O content. The TSDC curve showed two peaks near room temperature. Both of the peaks gradually shifted toward lower temperature with increasing K2O content. By adding KI to the potassium borate glasses, the TSDC attributed to potassium ions can be observed but not to iodine. However, when the DC was measured at above 400K, the current first increased and then decreased along with further increases in iodine content. Summarizing these facts, it is suggested that potassium ions bound in the glass network alter the long range mobility of ions with increasing temperature. While iodine is bound in the glass network, it may act as a dilator upon the glass network, enabling the potassium ions to move easily migrate about the network.