The electrochemical behavior of Ti(III) ions in a eutectic KF-KCl molten salt was investigated using cyclic voltammetry, square wave voltammetry, and chronoamperometry at 923 K. Ti(III) ions were produced by the addition of 0.50 mol% of K 2 TiF 6 and 0.33 mol% of Ti sponge to the melt. The reduction of Ti(III) ions to metallic Ti was observed as a single 3-electron wave around 0.33 V vs. K + /K in the square-wave voltammogram. The electrodeposition was conducted at a Mo electrode by galvanostatic electrolysis at −50 mA cm −2 for 20 min. The deposits were confirmed to be compact and adherent Ti metal films by scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction analysis. The oxidation of Ti(III) to Ti(IV) was observed at 1.82 V vs. K + /K as a reversible electrochemical process. The diffusion coefficient of Ti(III) ions was determined to be 3.9 × 10 −5 cm 2 s −1 .

A new method of electrodeposition of Ti using a water-soluble KF-KCl molten salt electrolyte has been proposed. The electrochemical behaviors of Ti(III) ions in a KF-KCl molten salt to which 0.1 mol% K 2 TiF 6 and an excess amount of sponge Ti were added have been investigated by cyclic voltammetry at 923 K. Anodic currents corresponding to the oxidation of Ti(III) ions were observed from 1.5 V (vs. K + /K) at a glass-like carbon rod electrode. In the negative potential region, cathodic currents were seen from 0.3 V, indicating the deposition of Ti metal from Ti(III) ions. When a nickel ag electrode was used, cathodic currents due to the formation of Ti-Ni alloys were observed, in addition to the current of deposition of Ti metal. The analyses of the electrodeposits by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry con rmed that dense and smooth lms of Ti metal with 20 μm thickness were obtained at current densities of 2.5 × 10

The electrodeposition of crystalline Si films on graphite substrates was investigated in KF-KCl molten salts at 1073 K. The optimum K2SiF6 concentration and current density to obtain adherent, compact, and smooth films were investigated using surface and cross-sectional scanning electron microscopy. The crystallinity of the deposited Si films was measured by Xray diffraction and electron backscatter diffraction techniques. By photoelectrochemical measurements in CH3CN-TBAPF6-Fc at room temperature, the Si film electrodeposited on the graphite substrate at 100 mA cm −2 for 30 min in molten KF-KCl-K2SiF6 (3.5 mol%) was found to be an n-type semiconductor. When SiCl4 was used as the Si source, the melt with a higher molar ratio of KF deposited smoother Si films on the graphite substrates. The Si films electrodeposited in molten KF-KCl after the introduction of SiCl4 gas (2.37 mol%) were confirmed to be p-type by photoelectrochemical measurements in CH3CN-TBAClO4-EVBr2.The characteristics of the electrodeposited Si film (p-type or n-type) is determined by the contaminating impurities (B, P, and Al).