Optical properties of switchable mirrors based on magnesium-calcium alloy thin films

Switchable mirrors based on magnesium-calcium alloy thin films were prepared using a direct-current magnetron sputtering method and their gasochromic properties have been investigated. Pd-capped Mg(1-z)Ca(z) (0.04 < z < 0.20) films showed excellent switchable mirror properties. The visible transmittance in the transparent state increased with Ca composition, z, and after reaching a maximum of similar to 46% at z similar to 0.06, the transmittance decreased gradually with increasing Ca composition. In the transparent state with z < 0.08, the optical transmittance spectra of these switchable mirrors were fairly flat in the visible range and their color looked completely neutral. The achromatic properties with high visible transmittance may be because the hydrogenated switchable mirrors are composed of MgH(2) and MgCaH(3.72) with grayish neutral color appearance.