Der Einflu� von Gitterst�rungen auf die �bergangstemperatur zur Supraleitung von Thallium

Abstract

The residual resistance of very pure Thallium wires was increased by plastic deformation at liquid Helium temperatures. The accompanying changes of the transition temperature to superconductivity were measured. With gradually growing resistance ratio the transition temperature decreases by some hundredths of a degree, reaches a minimum and increases up to the value of the undeformed specimen. This is a behaviour as observed for many other metals in dilute solid solution experiments, removing Tl from its role as an exception. Annealing the specimens at relative low temperatures will remove preferably point defects. This gives the possibility to study the influence of different types of lattice defects on the transition temperature. The results seem to indicate that point defects tend to increase the transition temperature, whereas extended imperfections, as e.g. dislocations, will decrease it.