Effect of dissolved oxygen on thermal oxidation in Ta2O5/Ta sandwiches

Abstract

Chemical analysis, structural investigations, and electrical capacitance measurements have been performed on Ta2O5/Ta foils annealed at 753K in air for different initial concentration of oxygen in Ta. It was shown that the initial concentration of oxygen in Ta plays a crucial role in formation of thermal nonstoichiometric oxide layer between tantalum and anodic Ta2O5, namely only Ta with low initial oxygen content covered with thin Ta2O5 layer is resistant to thermal oxidation. The obtained results may explain the degradation of real capacitors made of fine Ta powders.