Search for superconductivity in hydrides of TiZrNb, TiZrNbHf and TiZrNbHfTa equimolar alloys

We have prepared and investigated the superconducting equimolar alloys TiZrNb, TiZrNbHf and TiZrNbHfTa, which exhibit transition temperatures Tc between 6.4 K and 8.4 K, and examined the influence of hydrogenation on their superconductivity. The upper critical magnetic field Hc2 of alloys was estimated to be above 10 T, in agreement with previous studies of superconducting alloys of similar composition. On the other hand, the hydrogenation of alloys, some of which appear to be promising for hydrogen storage, lead to suppression of superconductivity in TiZrNb, TiZrNbHf and TiZrNbHfTa dihydrides and in TiZrNbHfTa monohydride, and no transition to superconducting state was observed therein above 2 K. A possible reason for this may be related to the high concentration of disorder (defects) in hydrides originating from the preparation method during which the starting alloy disintegrates into fine powder.