| Author/Editor | Milošev, I; Strehblow, HH; Gaberšček, M; Navinšek, B | |
| Title | Electrochemical oxidation of ZrN hard (PVD) coating studied by XPS | |
| Type | članek | |
| Source | Surf Interface Anal | |
| Vol. and No. | Letnik 24 | |
| Publication year | 1996 | |
| Volume | str. 448-58 | |
| Language | eng | |
| Abstract | Zirconium nitride (ZrN) belongs to the group of technologically important materials, namely hard tribological coatings. X-ray photoelectron spectroscopy (XPS) in combination with polarization experiments and electrochemical a.c. impedance spectroscopy has been used to study the composition, structure, thickness and electronic properties of layers formed by electrochemical oxidation of ZrN in phthalate buffer (pH 5.0). Results are compared to those obtained for layers formed by thermal oxidation at elevated temperature, i.e. ZrO2, as well as by air oxidation at room temperature. Electrochemical oxidation of ZrN to ZrO2 proceeds via the formation of a mixed oxynitride/oxide layer, which then tranforms into oxide at sufficiently positive potentials. Angle-resolved XPS measurements contribute to a better understanding of the in-depth layer structure. Exposure of ZrN to air at room temperature results in the formation of a thinoxynitride/oxide layer. The layer exhibitis a gradually changing in-depth distribution of various species, i.e. nitride, oxynitride and oxide. Analysis of XPS valence banc spectra ofers valuable information concenrning the electronic properties of investigated materials. The experimental valence band spectrum for ZrN correlates well with a theoretically calculated density-of-states diagram from the literature. In contrast to ZrN, which is a metallic conductor, layers formed by electrochemical oxidation, as well as by air oxidation, exhibit insulating properties. The insulating characters of the formed layers is supported also by a decreased curent density in subsequent cycles in cyclic voltamograms, as well as by the resistivity value (approximative 10 power on 12 omega - cm) calculated from a.c. impedance measurements. Therefore, the oxide layer formed on ZrN is stable and prevents further oxidation of the ZrN substrate. | |
| Descriptors | ALLOYS ZIRCONIUM MATERIALS TESTING SPECTROMETRY, X-RAY EMISSION ELECTROCHEMISTRY |