Mössbauer studies of O 4+ -bombarded Nb 3 Sn

Mossbauer spectra have been taken for Nb3Sn films on Hastelloy substrate bombarded with 25-MeV O4+ ions at fluences of 9.6 × 1015 and 4.0 × 1016 cm−2, and annealed at temperatures up to 1050 ‡C. The bombarded samples are found to contain highly damaged Nb3Sn and Nb6Sn5, and show superconducting transitions at 7.3 and 3.3 K, respectively. Annealing at higher temperatures does not restore the properties of the samples to those known for undamaged Nb3Sn films. The results rather indicate the presence of Nb3Sn and also Nb6Sn5 even after annealing at 850 ‡C. Annealing at 1050 ‡C seems to produce only regions of heavily damaged Nb3Sn.