Influence of Electrolytes in the Electrical Characteristics of Anodic Films on Tantalum

Abstract

The electrical characteristics of anodic oxide films formed on tantalum are investigated in anodes oxidized in the standard electrolytes for low-voltage (0.01% H3 PO4 in water) and high-voltage (same plus ethylene glycol) applications. It is found that small additions (about 0.1%) of certain organic acids such as citric acid to the above electrolytes greatly improves the leakage current, the scintillation voltage and the dielectric losses of tantalum capacitors. Furthermore, the use of these organic acids makes it possible to extend to higher voltages the use of the low-voltage electrolyte, ahd allows, in the case of the high-voltage electrolyte, a substantial diminution in the ethylene glycol concentration without impairing the characteristics of the resulting capacitors. Finally, the effect of the citric acid and the ethylene glycol in the anodizing electrolytes is discussed. © 1981, Gordon and Breach Science Publishers, Inc.