Green electrophoretic deposition of Bi₂O₃ coating

Due to significant band gap, high refractive index, dielectric permittivity, photoluminescence, dielectric permittivity prominent photoconductivity and photocatalytic activity, preparation of bismuth oxide (Bi₂O₃) coating has been a topic of extensive research and has potential applications involving microelectronics, sensor technology, opticalcoating, etc. In this study, the coating of nano-Bi₂O₃ was successfully fabricated via environment-friendly aqueous electrophoretic deposition (EPD). The EPD behavior of nano-Bi₂O₃ in aqueous dispersion was affected by the addition of nitric acid. Some factors influencing deposition behavior such as addition amount of nitric and particle concentration were investigated. For a typical EPD with nano-Bi₂O₃ of 1 g L⁻¹, the deposition rate increase with addition amount of nitric acid at first due to the improvement in surface charging of nano-Bi₂O₃ particles caused by absorption of hydrogen ion, and then would decline when higher concentration of nitric acid (>2 mM) was added due to serious water electrolysis. For the purpose of obtaining higher deposition rate of nano-Bi₂O₃ in aqueous suspension which was limited by lower deposition voltage, it was suggested to employ higher suspension concentration of Bi₂O₃. Correspondingly, higher addition amount of nitric acid is desired for sufficient surface charging for more nano-Bi₂O₃ particles. The environment-friendly aqueous deposition system provides a green EPD for successfully fabricating Bi₂O₃ coating with many potential applications.