Effect of the Presence of Structural Defects on the Superconducting Properties of (NbTa)_0.67(MoHfW)_0.33 and Nb-47wt%Ti

A comparison of the results of studies on the influence of structural defects on the critical parameters of superconductivity has been made for the high-entropy alloy (NbTa)(0.67)(MoHfW)(0.33) and for the conventional superconducting magnet material Nb-47wt%Ti. Positron annihilation lifetime spectroscopy (PALS), electrical resistivity, magnetization and magnetic susceptibility measurements were used. In addition, X-ray powder diffraction studies were performed on the high-entropy alloy (NbTa)(0.67)(MoHfW)(0.33). Due to the rapid cooling of the materials after melting in the arc furnace, they contain a higher concentration of structural defects compared to the heat-treated materials. Magnetic property measurements showed that both the critical temperatures T-c and the upper critical fields mu H-0(c2) of bulk superconductivity-related materials are improved in the presence of structural defects.