Nucleation and surface morphology of aluminum-lanthanum alloy electrodepsited in a LaCl3-saturated AlCl3-EtMeImCl room temperature molten salt

The cathodic polarization curve on a tungsten disk electrode was measured in a LaCl₃-saturated AlCl₃-EtMeImCl [1-ethyl-3-methylimidazolium chloride] melt (N=0.667: N is molar fraction of AlCl₃) at 298 K. The deposition overpotential of aluminum increases compared with the curve obtained before adding LaCl₃. It was found that the nucleation/growth process is instantaneous nucleation from chronoamperometric data. When galvanostatic electrolysis was performed in the LaCl₃-saturated melt, the strong orientation of (200) for the electrodeposits is observed at low current densities (≤7.5 mA cm⁻²). On the other hand, the normalized integrated intensity of XRD for (200) and (220) reflections has similar strength at high current densities (≥10.0 mA cm⁻²). The electodeposits become denser than those obtained in the original melt. In particular, very smooth surface is obtained in the case of 15.0 mA cm⁻² with stirring the bath.