Composition, morphology and electrical transport properties of Co–Pb electrodeposits

Abstract

-Bath compositions were elaborated for the codeposition of Co and Pb by taking into account the chemical compatibility of Co 2+ and Pb 2+ with the appropriate anions. Electrolytes containing either acetate, chloride or nitrate anions were tested, but only the acetate bath proved to be appropriate for the preparation of compact Co-Pb films. Deposits were obtained with constant current, with constant potential or by using various current and potential pulses in order to investigate the possibility of multilayer formation. The variation in deposit composition as a function of the deposition parameters was elucidated by using cyclic voltammetry, current transient measurements and gravimetry. X-ray diffraction (XRD) patterns recorded for two-pulse plated deposits revealed a nanocrystalline structure with grain sizes in the range 5 to 20 nm. The XRD peaks could be well indexed to pure face-centered cubic Co and Pb, indicating that the Pb codeposited with Co is not dissolved in Co but is segregated. Both the d.c.-plated and the two-pulse plated deposits exhibited anisotropic magnetoresistance without an indication for a noticeable giant magnetoresistance contribution. This means that the observed magnetoresistance arises from spindependent electron scattering events dominantly within the sufficiently large Co regions and not along electron paths between two Co regions via the Pb regions. Low-temperature resistivity measurements revealed a superconducting transition slightly below that of pure Pb. This may be ascribed to a proximity effect: the ferromagnetic Co grains suppress somewhat the superconductivity of the Pb phase due to the nanoscale phase mixture of the two constituents.

Electrodeposition of Lead–Cobalt Anodes: The Effect of Electrolyte pH on Film Properties

“…Co 2+ (aq) +2H + +4e − → Co (s) +H 2(ads) [4] For solutions at a pH of between 4 and 6, Co 2+ reduction could proceed through the formation of Co(OH) 2 in the solution-electrode interface, according to Eqs. 5-8: 13,14 2H 2 O + 2e − → 2OH − (aq) +H 2(g) [5] Co 2+ (aq) +2OH − (aq) → Co(OH) 2(s) [6] Co(OH) 2(s) +2e − → Co (s) +2OH − (aq) [7] where the global reaction can be written as:…”

“…Electrodeposition has been reported as the best alternative to combine these two elements. 7 Limited literature has focused on the preparation and behavior of different Pb-Co-coated anodes in acidic media. 3,4,7 In some studies, the Pb-Co coatings electrocatalyse the OER, decrease the required overpotential, and exhibit a lower degradation rate compared with conventional Pb-Ca-Sn anodes.…”

“…7 Limited literature has focused on the preparation and behavior of different Pb-Co-coated anodes in acidic media. 3,4,7 In some studies, the Pb-Co coatings electrocatalyse the OER, decrease the required overpotential, and exhibit a lower degradation rate compared with conventional Pb-Ca-Sn anodes. 3,4 Many factors influence the electrodeposition process such as temperature, solution pH, concentration of electroactive species in the electrolyte, substrate material, and the use or not of complexing agents.…”

Influence of Pb Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

“…In a recent work [18], we have investigated the codeposition of Co and Pb from acetate-, chloride-and nitrate-based baths out of which the acetate bath only yielded compact Co-Pb deposits. Although compact Co/Cu(Pb) multilayers could be successfully prepared from such a bath, the magnetoresistance measurements performed on these samples have not provided reliably reproducible results.…”

“…As a next step, we intended to carry out a similar study in order to explore the influence of Pb when added as surfactant to the Cu spacer layer of electrodeposited Co/Cu multilayers. In a recent work, 18 we have investigated the codeposition of Co and Pb from acetate-, chloride-and nitrate-based baths out of which the acetate bath only yielded compact Co-Pb deposits. Although compact Co/Cu(Pb) multilayers could be successfully prepared from such a bath, the magnetoresistance measurements performed on these samples have not provided reliably reproducible results.…”