Influence of B atom diameter on annealing recovery rates of superconducting transition temperatures in irradiated A-15 (A3B) compounds

It has recently been shown that the superconducting properties of Nb-base A-15 compounds, A3B, are severely degraded when exposed to high-energy (E>1 MeV) neutron irradiation at ambient reactor temperatures. In each case, superconducting transition temperatures, Tsub(c), and the Bragg Williams order parameters, S, were observed to decrease steadily with irradiations in excess of 1018 nvt. During irradiation the A-15 structure is retained and subsequent isothermal annealing restores almost completely the compound's original Tsub(c) value. In this letter a correlation between B atom diameter and the recovery rates of Tsub(c) for the irradiated materials Nb3Ge, Nb3Ga, Nb3Al and Nb3Sn is reported. (Auth.)