Anna-Maria Janner

Cycling durability of switchable mirrors

Abstract The remarkable optical properties of switchable mirrors, i.e. the ability of lanthanide–magnesium films to switch reversibly between reflecting and transparent states by changing the hydrogen concentration, are interesting for several applications. Since for any application a high cycling durability is necessary, we have studied the durability of various, differently prepared, switchable mirrors. As a model system we have chosen to switch in a 1 M KOH solution. Typical degeneration features that were found included slower kinetics, oxidation and delamination upon cycling of the switchable mirror. Of the various attempts to improve the cycle lifetime, we obtained the best results by using a switchable mirror loaded with hydrogen during deposition.

A Photoelectrochemical Study of the GdMg Hydride Switchable Mirror

A significant chemical stability has allowed us to perform photoelectrochemical measurements on the semiconducting state of the GdMg hydride system. With electrical impedance spectroscopy we confirm that GdMg hydride in the transparent state is an n-type semiconductor. The donor density was estimated to be 5 3 1021 cm23. Impedance measurements give information about the potential distribution at the semiconductor/solution interface. Photocurrent was observed in the transparent state. It is proposed that photoanodic etching of the GdMg hydride at high light intensities occurs along grain boundaries, leading to inhomogeneous destruction of the film.