Study and preparation of silver electrodeposits at negative potentials

Electrodeposition of silver films, potentially useful as a matrix for cobalt–silver magnetoresistive materials, has been studied. Silver electrodeposition at negative potentials has been analyzed in order to attain deposition potentials next to those of cobalt. The study of the process in an acidic perchlorate medium showed the necessity of using a complexing agent to shift both silver electrodeposition and proton reduction to negative potentials. This was achieved by adding thiourea which allowed silver electrodeposition in a wide range of potentials where secondary proton reduction process was not significant. Scanning electron microscopy analysis showed that the presence of thiourea in the bath was beneficial, since the silver films completely coated the substrate. Furthermore, the silver deposits obtained were compact, uniform, fine grained but rough. To further improve deposit quality, organic (sodium gluconate) and inorganic (boric acid) substances were added to the electrolytic bath, revealing a substantial improvement in the deposits obtained. Thus, conditions favourable to silver–cobalt codeposition have been determined.