Plansee AG of Reutte, Austria, reports that it is supplying tungsten and tungsten-nickel sputtering targets to customers to create electrochromic layers on ‘smart window’ glass. The company states that a reactive sputtering process is used to create the tungsten oxide or tungsten-nickel oxide layer from the sputtering targets.
Under normal circumstances this oxide layer is transparent. The colour changes from transparent through to dark blue entirely automatically, depending on how bright the sun is, or by the application of a DC voltage.
This voltage makes positively charged lithium ions migrate into the electrochromic layer on the glass, which then become dark blue, and prevents buildings from becoming too hot.