This paper presents recent results from authors’ lab on the pulsed electrodeposition of refractory metals from ionic liquids (ILs). Special focus will be given to the refractory metals tantalum and niobium (Fig. 1) as they are promising candidates for surface finishings with extremely high corrosion resistance.

We could show that by varying the pulse plating parameters (such as the potential of the on pulse, as well as the frequency and the duty cycle) one can optimize the morphology of the deposits. Thus, experimental conditions have been identified with which uniform and crack-free deposits can be obtained. Due to the high viscosity and low conductivity of the ionic liquids, the useful frequency range for pulse plating is somewhat different from one knows from aqueous electrolytes. Moreover, the effect of the temperature (from 25°C till 170°C) on the properties of the deposits has also been investigated and will be discussed in this paper.

Fig. 1. Nb layer electrodeposited on Ti substrates from 0.5M NbF₅ in 1‑butyl‑1‑methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide at RT; Deposition conditions: 1 min @-1V; 1 min @ -2.5V, sequence repeated for 2500x.