Ionic Conduction at High Electric Field Strengths in Tantalum Pentoxide

Abstract

Polarization of the cell Ta|Ta₂O₅|Solution|Pt sets up a very high electric field strength in the oxide and ionic conduction (resulting in growth of the oxide film) occurs with negligible electronic conduction. With this cell measurements of field strength and current density have been made in the temperature range -63 to + 90°C. These results are incompatible with single barrier control in which space charge is neglected but are consistent with a theory proposed by Dewald in 1955 in which space charge due to ions in transit causes the field in the oxide to vary through its thickness, so that barriers near the metal interface and within the oxide both play a part in controlling the rate of oxide formation.