Study of the Superconducting Transition Temperature in Dilute Thallium Solid Solutions

The superconducting transition temperature, $T_c$, has been measured for dilute solid solutions of indium, bismuth, and lead in thallium. The transition temperature is found to increase in all cases thus exhibiting a behavior opposite to that observed by Serin, Lynton, and co-workers in their studies of solid solutions of tin, indium, and aluminum. Some loss in residual impurity scattering which occurs upon annealing suggests the migration of solute atoms to grain boundaries in the dilute alloys.