Electrochromic nickel oxyhydroxide films were formed by an electrodeposition method from 0.005 M NiSO4+0.015 M (NH4)SO4 solution, and their memory characteristics, response time and operation lifetime were investigated. The films prepared were porous with a network structure. They were colorless and transparent in a lower oxidation state [Ni(OH)2], but were dark brown in a higher oxidation state [NiOOH]. By heat-treating the films at 250degC for 15 minutes, electrochromic characteristics such as the operation lifetime could be remarkable improved.

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