High electric field conduction in low-alkali boroaluminosilicate glass

It is important to understand electronic and ionic transport in low-alkali boroaluminosilicate glass, which is a promising dielectric for high energy density capacitors. Electric field, thickness, and temperature dependence of the leakage currents for low-alkali boroaluminosilicate (Schott AF 45) were all investigated to elucidate potential conduction mechanisms under high electric field. The bulk conductivity ranged from 10⁻¹⁶ S/m at room temperature to 10⁻¹² S/m at 200 °C. It was also found that conduction significantly increased with electric field and that a single conduction mechanism does not adequately describe leakage current data over wide electric field and temperature ranges. From the systematic analysis applied here we conclude that the conduction was governed by a combination of multiple conduction mechanisms. It is suggested that ion hopping conduction by the sodium ion migration dominated the conduction at the initial stage followed by space-charge-limited conduction from sodium ion depleted regions where electric field is enhanced.