Optical switching durability of switchable mirrors based on magnesium–yttrium alloy thin films

Switchable mirrors based on magnesium–yttrium alloy thin films were prepared using a direct-current magnetron sputtering method. The optical switching durability between reflective and transparent states using a gasochromic method has been investigated. Pd-capped Mg1−zYz (0.14<z<0.81) films showed excellent switchable mirror properties. The switching durability increased with Y composition, z, and reached over 10,000 cycles at z>0.5. The mirrors with the Y composition in the wide range of 0.27–0.70 have visible transmittance values of about 35% in the transparent state. The difference in visible transmittance between the reflective and transparent states decreased with z, especially over 0.7. In the transparent state, all prepared switchable mirrors had relatively flat optical transmittance spectra in the visible range and showed nearly neutral color appearance. Thus, the optimal Y composition is in the range of 0.5–0.7 for switchable mirrors with high switching durability and large dynamic range between the reflective and transparent states.