Thermal-neutron-induced Gd-point defects in GdBa 2Cu 3O 7− δ ceramics

Abstract

The main purpose of this work is to study the role of point defects for flux pinning in high temperature superconductors. In order to do so, two ceramic samples of superconducting GdBa 2Cu 3O 7− δ (Gd-123), one containing 155 Gd ( σ=61000 b) and one 160 Gd ( σ=0.77 b), were irradiated in the thermal column of the TRIGA reactor in Vienna. Both samples were subjected to thermal neutron fluences of 7×10 17, 7×10 18, 7×10 19, 2.66×10 20, 4.77×10 20, and 9.75×10 20 m −2. After each irradiation step the superconducting transition temperature T c was measured and the critical current densities J c were calculated from magnetization loops using the Bean model. We find that T c remains unchanged in both samples within experimental uncertainty. J c does not change in 160 Gd -123, whereas it shows signs of an enhancement in 155 Gd -123 after the last irradiation step. Hence, the overall contribution of point defects to flux pinning in 123-superconductors is small.