Electrodeposition of silicon, titanium and tungsten from molten fluoride-chloride systems
Molten salts are expected to be used for smelting and recycling of various metals because of their wide electrochemical window and ability to dissolve various metal salts. The demand for silicon (Si) is expected to increase owing to the increasing demand for Si solar cells. Titanium (Ti) plating is valuable owing to its high corrosion resistance and biocompatibility. Tungsten (W) is utilized in many fields because of its high heat resistance and hardness and is expected to be used as a heat-resistant material in fusion reactors. We propose that molten KF–KCl and CsF–CsCl are novel molten salt systems for the electrodeposition of Si, Ti, and W. Photoresponsive n- and p-type semiconducting Si was electrodeposited. We electrodeposited Ti which had no cracks or voids and corrosion resistance to seawater. α-W films with a rough surface were obtained with a K-based system, but when the temperature was lowered by using a Cs-based system, β-W films with a mirror surface were obtained. This is the first time that β-W on the order of several micrometers has been produced in a single phase.