Electrochromic nickel-oxide-based coatings made by reactive dc magnetron sputtering: Preparation and optical properties

NiOx films were made by dc magnetron sputtering of Ni in O2 at a rate of 0.15 nm s−1. The grain size was ∼10 nm and the crystal structure was cubic. Electrochemical hydration, and ensuing conversion to electrochromic NiOxHy, took place in KOH. Spectrophotometric measurements in the 0.35–2.5-μm range showed that it took 100 color-bleach cycles to establish a fully bleached state. When removed from the KOH electrolyte, a colored NiOxHy film increased its transmittance by 1% per h. The luminous and solar transmittance could be varied between 80% and 20% and between 74% and 29%, respectively.