XPS and GDOES Characterization of Porous Coating Enriched with Copper and Calcium Obtained on Tantalum via Plasma Electrolytic Oxidation

XPS and GDOES characterizations of porous coatings on tantalum after Plasma Electrolytic Oxidation (PEO) at 450 V for 3 minutes in electrolyte containing concentrated (85%) phosphoric acid with calcium nitrate and copper (II) nitrate are described. Based on the obtained data, it may be concluded that the PEO coating consists of tantalum (Ta5+), calcium (Ca2+), copper (Cu2+ and Cu+), and phosphates (PO43-). It has to be pointed out that copper and calcium are distributed throughout the volume. The authors also propose a new model of PEO, based on the derivative of GDOES signals with sputtering time.