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Title In situ XPS investigation of the baking effect on the surface oxide structure formed on niobium sheets used in superconducting RF cavity production.
Type Poster materials / surface effects
Abstract Investigations were performed for two types of Nb samples prepared by the standard treatments used for the niobium RF cavity production, electro-polishing (EP) and buffered chemical polishing (BCP). The chemical structure of thin oxide films naturally formed on the Nb surface changed on baking. It was observed in situ by means of the X-ray Photoelectron Spectroscopy (XPS). The experiments were carried out in the temperature range from 100 to 180 degrees Celsius for 120-hour periods of time. It was found out that the film thickness for the EP samples was greater than that for the BCP ones. The Angle-Resolved XPS (AR-XPS) analyses indicated that the oxide films consisted of the thicker external Nb2O5 layer and the much thinner NbO2 and NbO phases placed below it. The Nb2O5 phase progressively dissociated and the NbO2 and NbO oxides developed on baking. This effect was hardly noticeable at 100 C but considerably revealed at higher temperatures. At the temperature of 180 C the NbC phase was formed at a certain stage of the oxide layer evolution and then it developed on further baking. While the tendency of the process was the same for the both EP and BCP samples, the kinetics of the surface oxide layer evolution was much faster for the BCP samples than for the EP ones.

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Kowalski K AGH University of Science and Technology, Krakow, Poland
Bernasik A AGH University of Science and Technology, Krakow, Poland
Singer W DESY, Hamburg, Germany
Singer X DESY, Hamburg, Germany
Camra J Jagellonian University, Krakow, Poland

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