Mechanism of the local destruction of the amorphous Ta2O5 layer on the surface of a tantalum anode

In the present work, a mechanism of the destruction of amorphous tantalum oxide Ta₂O₅ on the tantalum anode surface is suggested based on high absorption properties of tantalum. The data of analysis of the morphological peculiarities of the defective areas of the surface layers show that the destruction of the amorphous film occurs due to the growth of a pyramid-shaped defect; the pyramidal defect is not coherent with amorphous surface Ta₂O₅, and it is not a product of its crystallization. The nucleation and growth of the “pyramid” occurs due to the directed movement of oxygen during the oxidation of the tantalum surface along the grain boundaries to the region of triple junctions of the tantalum matrix with the subsequent local formation of crystalline Ta₂O₅. The suggested mechanism offig destruction can be realized when high-purity tantalum powders are used.