Oxidation State of Anodic Tantalum Oxide after Heat-Treatment

During heat‐treatment of anodic in vacuum (10 −5 Torr) at temperatures in the range from 200° to 700°C oxygen exchange between the anodic oxide, the Ta substrate, and the atmosphere was observed. Galvanostatic reanodization experiments resulted in potential‐time (charge) curves which could be used to determine the oxidation state of heat‐treated as a function of the distance from the electrolyte/oxide interface into the oxide. Profiles of the oxidation state across the oxide were measured for tantalum oxide anodized in and after heat‐treatment at 10 −5 Torr and 500°C. Of several experimental variables, the time of heat‐treatment and the oxide thickness were chosen to illustrate the method of determining oxidation state profiles for the case of heat‐treatment in vacuum. In all cases treated in this paper the reduction was carried out to the extent that the oxide as a whole exhibited high electronic conductivity.