Investigation of the mechanism of electrosynthesis of the superconductor Ba_1-xK_xBiO₃

Cyclic voltammetry has been used to investigate the electrodeposition of the superconducting material, Ba_1-xK_xBiO₃. Reactions occurring at a Pt substrate electrode over a wide potential range have been assigned. Evidence has been found for time-dependent (cycle number) electrochemical behavior. High-quality superconducting crystals can be obtained only when the potential of the electrode is held in the region of predominantly kinetic control. The Bi^III to Bi^V oxidation appears as two peaks during the anodic scan. Reproducible cyclic voltammograms were obtained only after the KOH flux containing Ba(OH)₂ and Bi₂O₃ was equilibrated for 24 h under a water-saturated argon atmosphere. High-quality superconductive crystals are obtained only when the deposition potential is on the rising portion of the Bi^III to Bi^IV oxidation peak.