An aging effect and its origin in GdBCO thin films

: Schlesier K, Huhtinen H, Granroth S, Paturi P

: 2010

: Journal of Physics: Conference Series

: 9TH EUROPEAN CONFERENCE ON APPLIED SUPERCONDUCTIVITY (EUCAS 09)

: J PHYS CONF SER

: ARTN 012036

: 234

: 9

: 1742-6588

DOI: https://doi.org/10.1088/1742-6596/234/1/012036

An aging effect investigation was made for GdBa2Cu3O7 (GdBCO) thin films grown on SrTiO3 (001) substrates with pulsed laser deposition (PLD) method from nanograined targets. The films were cut into two pieces where one piece was coated with gold cap layer while the other was left without coating. Both pieces were kept in ambient air during the half year measurement period. Magnetization measurements as well as phase purity, lattice parameter, oxygen effect and depth structure determination with x-ray diffraction (XRD) were made in one month interval. For structure and oxygen content, x-ray photoelectron spectroscopy measurements (XPS) were done in the beginning and in the end of the period. A reduction of the critical temperature and the critical current density, J(c), was found in the gold coated GdBCO film in ambient air in course of time. A smaller decrease of J(c) was detected in uncoated GdBCO. No development of impurity phase, increase of a-orientation or reduction of the pinning structure was detected in uncoated GdBCO. However, a small development of impurity phase was found in gold coated GdBCO. The diminution of T-c and J(c) is concluded to originate from oxygen release. No such a phenomenon was found in YBa2Cu3O7. We conclude that gold is not a proper cap layer at least for some applications.