The effect of lanthanum chloride on the electrocrystallization behavior of cobalt and grain refinement in deposition layers

This study investigates the effect of different concentrations of lanthanum chloride (LaCl 3 ) on the grain refinement of cobalt deposition layers during the electrochemical deposition process in industrial electrolytes. The impact of different LaCl 3 concentrations on cobalt electrodeposition behavior was analyzed using the Liner sweep voltammetry curve (LSV), Cyclic voltammetry curve (CV), and Chronoamperometry curve (CA). The microstructure morphology and grain size of the deposition layers were analyzed using scanning electron microscopy and atomic force microscopy and the preferred orientation and crystal structure were analyzed using X-ray diffraction. The results show that the addition of different concentrations of LaCl 3 to the industrial electrolyte leads to a negative shift in the starting deposition potential of cobalt, an increase in cathode polarization degree, an increase in overpotential, a shortened nucleation relaxation time t m and an accelerated nucleation rate during cobalt electrodeposition, resulting in grain refinement of the deposition layers. However, the addition of LaCl 3 does not change the cobalt electrocrystallization mechanism, nor does it alter the crystal structure of the cobalt deposition layers, which remain in a close-packed hexagonal structure (HCP). When 0.2 g/L LaCl 3 is added, the grain growth orientation changes from the (11\(\stackrel{\text{-}}{\text{2}}\)0) plane to the (11\(\stackrel{\text{-}}{\text{2}}\)0) and (10\(\stackrel{\text{-}}{\text{1}}\)0) planes, resulting in a uniform distribution of grain size and obvious grain refinement of the deposition layers.