Magnesium–titanium alloy thin-film switchable mirrors

In this paper, we show gasochromic and electrochromic switching properties of Pd top capped magnesium–titanium (Mg–Ti) thin films prepared by DC magnetron sputtering. These films show excellent switchable mirror properties. By exposing to 4% H2 in Ar, Pd (4 nm)/Mg0.82Ti0.18 (40 nm) film changed from the metallic state to the transparent state drastically within 5 s. By exposing to air, it goes back to the metallic state within 60 s. The transmittance spectrum in the hydride state is quite flat in the wavelength range from 400 to 2500 nm. It looks complete color neutral and its chromaticity coordinates are x=0.326 and y=0.340. Simple electrochromic device of Mg–Ti thin film using a liquid electrolyte works very well. It can be switched between the mirror state and the color-neutral transparent state.