The feasibility of growing nanostructured films composed of cobalt and yttrium hydroxide/oxide phases by electrodeposition is demonstrated. Particle-free aqueous solutions containing YCl3 and CoCl2 salts and glycine were used. The incorporation of yttrium compounds into the cobalt deposit was achieved using pulse deposition (ton = 0.1 ms, toff = 0.9 ms) and for cathodic pulses higher than -500 mA cm -2. Deposits obtained were crack-free, typically with 1-5 wt% yttrium, and exhibited morphologies markedly different from the ones shown by pure cobalt deposits. Moreover, yttrium-rich films (up to 30 wt% Y) could be deposited under certain conditions, though incipient cracking developed in this case. X-ray photoelectron spectroscopy analyses revealed that Y(OH) 3/Y2O3 compounds were present in the films. From the structural viewpoint, the composites exhibited a partially amorphous/nanocrystalline character, with the crystalline fractions originating from the hexagonal-close packed structure of α-Co. A refinement of the α-Co crystallite size was observed in deposits containing higher weight percentage of yttrium compounds. Nanoindentation tests revealed that hardness increased with the yttrium content. This result can be explained by taking into account both the presence of intrinsically hard oxide phases and the effects promoted by incorporation of yttrium hydroxides/oxides on the α-Co matrix (namely, grain-refining and higher concentration of stacking faults). © 2011 Elsevier Ltd. All rights reserved.
- Pulse deposition
- X-ray photoelectron spectroscopy
- Yttrium hydroxide/oxide