Grain-boundary effects on the resistivity of zinc-doped Y-Ba-Cu-O

The electrical resistivity of the granular superconductors, YBa2Cu3-xZnxO7-y with x=0.05, 0.075, 0.1, 0.15, and 0.2, has been measured precisely below the midpoint of the superconducting transition. The expression for electrical resistivity due to Ausloos fits the data over a small temperature region. Besides, the value estimated for the average volume of the intergranular junction on the basis of the above fit is about a few thousands of A3 which is physically not reasonable. On the other hand, the results obtained could be explained better on the basis of a model that assumes that the fraction of the grain boundaries not becoming superconducting at a temperature T follows a Gaussian distribution. © 1989 The American Physical Society.