Virginie Mercier

Toward solid-state switchable mirrors using a zirconium oxide proton conductor

The unique optical properties of magnesium rare-earth alloys are interesting for making new types of solid-state electrochromic devices, based on hydrogen transport. These devices can reversibly switch between a transparent and a reflective state, when a potential difference is applied. The all-solid state devices presently studied involve a zirconium oxide proton conductor. This paper discusses the deposition and preliminary characterisation of the solid-state electrolyte. It also gives some information about the performance of a symmetrical GdMg device tested in a hydrogen gas atmosphere. This stack is composed of a GdMgH x /Pd bottom electrode, a ZrO 2 (H 2 O) x [H 2 ] y proton conductor and a Pd/GdMgH y /Pd top-electrode.

Solid state Gd–Mg electrochromic devices with ZrO2Hx electrolyte

A hydrogen based device, which consists mainly of a GdMgH5 electrochromic layer, a ZrO2Hx electrolyte and a WO3 electrochromic counter electrode, was made. When a positive voltage is applied to the GdMgH5 layer, the hydrogen moves towards the WO3 layer. The latter becomes blue while the GdMgH5 layer becomes metallic (GdMgH2), resulting in a non-transparent stack. When a negative voltage is applied to the GdMgH2 layer, the hydrogen moves back to the GdMgH2 layer. Both are eletrochromic layers and therefore the stack becomes transparent again. The devices switch reversibly up to 500 times with switching times in the order of minutes. This paper deals with the deposition and in-situ loading of the devices with hydrogen and contains some preliminary information on the switching behaviour and optical properties.

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.