Electrodeposition of Fe-Tb Alloys from an Aqueous Electrolyte

Abstract

DC electrodeposition of iron-rich terbium alloys on copper electrodes has been achieved using aqueous citrate solutions. Experiments were carried out in a Hull cell to examine the influence of a wide current density range on the composition and thickness of Fe-Tb alloys. Bright, gray, thin Fe-Tb alloy films were obtained with low current efficiencies. Energy dispersive spectroscopic analysis indicated that Na, S, and O impurities were incorporated in the film. The experimental results demonstrated, for the first time, that Fe promoted terbium electrodeposition. Thus, the alloy codeposition mechanism was classified as the induced type. © 2000 The Electrochemical Society. S1099-0062(00)04-110-9. All rights reserved. Electrodeposited terbium alloys are of interest for their potential use as thin film magnetostrictive, smart materials with applications for remote sensing and actuating. Bulk Terfenol, TbFe 2 , and Terfenol-D, Tb 0.3 Dy 0.7 Fe 1.9 , exhibit giant magnetostriction at room temperature with yield displacements on the order of 1000 ppm under modest magnetic fields (~1 kOe). 1,2 These materials are currently manufactured by bulk metallurgical processes 3,4 and thin film deposits have been realized using vapor deposition techniques. [5][6][7][8][9] To our knowledge there is only one report of Fe-Tb alloy electrodeposition from an aqueous solution. Lim et al. 10 investigated the electrodeposition of Fe-Tb-O films from a tartrate electrolyte with ac currents and measured their magnetic properties. This paper reports our recent findings on the dc electrodeposition of Fe-Tb alloys from a citrate electrolyte. The qualitative features of the electrodeposition mechanism are addressed.The challenge in electrodepositing rare earth metals stems from their electronegative oxidation-reduction potentials (e.g., Tb +3 + 3e -} Tb; -2.28 V). 11 Such a negative potential can limit electrodeposition from aqueous solutions, because water decomposes at a much higher potential (e.g., 2H 2 O + 4e -} 2 OH -+ H 2 ; -0.828 V). 11 Either complexing agents must be used to move the reduction potentials to a more favorable region in an aqueous solution or a different electrolyte can be employed (e.g., organic or fused salt). In the literature, both methods have been reported for a variety of rare earth elemental and alloy electrodepositions.Aqueous electrolytes have been used for the reduction of Sm, 12 La, 13 Dy-Ba-Cu, 14 and Nd 2 CuO 4 . 15 Lokhande and Jundhale 12 investigated the electrodeposition of elemental samarium films from aqueous acidic and alkaline baths with tartaric acid. The deposition potentials were found to be substrate and complexing agent dependent. Lokhande et al. 13 also reported the electrodeposition of lanthanum from aqueous solutions on different substrates. Sodium citrate was found to be a suitable complexing agent for lanthanum deposition. Concerning alloy rare earth deposits, Pawar and Pendse 14 carried out Dy-Ba-Cu electrodeposition from an aqueous bath. They obtained Dy-Ba-Cu alloys with thicknesses of 3-...

Electrolytic synthesis of TbFe2 from Tb4O7 and Fe2O3 powders in molten CaCl2

“…At present, these materials are mainly manufactured by pyrometallurgical processes in which separately extracted Fe, Tb and Dy metals are alloyed or compounded by melting processes under inert gas protection [3]. Electro-deposition of Tb-Fe alloy films from aqueous or organic solutions at room temperature was reported [4][5][6], but may be unsuitable for mass production because of the limited solubility of rare earth compounds in the used solutions. It also suffers from low current efficiency and low diffusion coefficient of Tb in Fe at room temperature.…”

Single step electrosynthesis of NiMnGa alloys

“…Despite extensive research on the integration of small architectures made of complex alloys, fabrication processes compatible with small systems manufacturing have not been fully established. Such is the case with Nd-based permanent magnets [3], giant magnetostrictive Terfenol-D [4], and ferromagnetic shape memory alloys, such as NiMnGa [5]. Bulk fabrication techniques are often employed, which may involve melt spinning, crushing and milling, sintering, ingot synthesis, and processing at high temperatures [3,4,6].…”

“…Such is the case with Nd-based permanent magnets [3], giant magnetostrictive Terfenol-D [4], and ferromagnetic shape memory alloys, such as NiMnGa [5]. Bulk fabrication techniques are often employed, which may involve melt spinning, crushing and milling, sintering, ingot synthesis, and processing at high temperatures [3,4,6]. Bottom-up methods based on physical vapor deposition techniques have also been employed for multi-alloy fabrication due to their compatibility with micro-and nanosystems processing [1,7,8].…”

Preparation of La-Cr Perovskite Coating Using Electrodeposition Method

“…The evolution potentials were found to be substated-and complex agent-dependent. Gong et al 17 reported the electrodeposition of Fe-Tb alloys from aqueous citrate solutions. Thin Fe-Tb films were obtained, but with low current efficiencies.…”