Sequential n-fold (n ? 4) Electrodeposition of YBa2Cu3O7­? HTSC Films on Silver Substrates

Abstract

Electrodeposition of multimetallic films at room temperature on metallic substrates followed by oxidation at high temperature (-900'C) has often been employed to prepare high temperature superconducting (HTSC) films. A difficulty with this otherwise cheap and simple process is that the degree of surface covering is usually not very high. We have attempted to remediate this problem by sequentially repeating the deposition process on the same film. In this way, we have improved quite markedly critical current density (Jo) of films obtained on Silver substrates. To quote some figures, J, at 1 T is -400 A/cm 2 after the first deposition/oxidation process and it increases to -2 000 A/cm 2 after the fourth one. The evolution of the morphology of the films has been followed by means of scanning electron microscopy (SEM). It shows that, although the degree of surface coverage never attains 100 %, a substantial proportion of the substrate is well coated. We have also studied the influence of mechanical pressure on the metallic film before the thermal treatment; after the fourth deposition, a pressure of-15 KBar was applied. In this case a -7% increase in Jc was observed and the density after compression (6.98 g/cm 3) attains almost 100 % ofthe theoretical value for YBa2Cu307.6 (Ybacuo).