Electrodeposition of mirror surface β-W films in molten CsF–CsCl–WO3

Abstract In this study we report, for the first time, a thick β-W film with a mirror-like surface prepared through electrodeposition involving a CsF–CsCl eutectic melt combined with 2.0 mol% of WO3 at 773 K. A smooth-surfaced β-W film with a thickness of 13 µm was obtained when galvanostatic electrolysis was performed at −4 mA cm−2. X-ray diffraction analysis revealed that the obtained β-W films have a strong preferred orientation along the {111} plane, which becomes stronger with decreasing current density. Surface and cross-sectional morphologies observed through scanning electron microscopy indicated that increasing the current density caused the growth of the electrodeposit to change from the field-oriented texture type to the unoriented dispersion type, in accordance with Fischer’s classification of electrodeposition. To the best of our knowledge, this is the first time that mirror-like metal films have been electrodeposited in a high temperature molten salt, not only for tungsten but for any metal.