2010 Volume 10 Issue Special_Issue Pages s215-s220
We have investigated the electrochemical formation and phase control of La-Ni alloy films in LiCl-KCl eutectic melts added LaCl3 (0.50 mol%) at 723 K.
Open-circuit potentiometry was carried out with a Ni electrode after depositing La metal by potentiostatic electrolysis at 0.40 V (vs. Li+ / Li) for 60 s. There were four potential plateaus at (a) 0.52 V, (b) 0.62 V, (c) 0.75 V and (d) 1.42 V, respectively. The observed potential plateaus were considered to correspond to different coexisting La-Ni phases, respectively. Based on the result of open-circuit potentiometry, an alloy sample was prepared by potentiostatic electrolysis at 0.48 V for 1 h at 723 K. From the XRD pattern of the sample, the alloy phase was identified as only La7Ni16.
In order to form various La-Ni phases, selective anodic dissolution of La from the formed La7Ni16 film was conducted at 0.58 V, 0.68 V, 1.00 V and 1.80 V, respectively. The La7Ni16 film with thickness of 3.5 μm was prepared by potentiostatic electrolysis at 0.48 V for 1 h. In the sample obtained at 0.58 V for 1 h, the existence of LaNi3 was clearly seen. The alloy film had some pores, which was thought to be caused by the volume change during the anodic polarization. Phase of the sample obtained at 0.68 V for 1 h was La2Ni7 by XRD analysis. The La2Ni7 film also has some pores. The sample obtained at 1.00 V for 2 h was found to be LaNi5. The obtained film contained more micropores than the LaNi3 and La2Ni7. The sample obtained at 1.80 V for 2 h was delanthanized to Ni. The obtained film was about 3.0 μm and had a porous structure.
