OPTICAL SWITCHING OF Y-HYDRIDE THIN-FILM ELECTRODES - A REMARKABLE ELECTROCHROMIC PHENOMENON

The optical appearance of yttrium thin film electrodes can be electroc hemically switched from mirrorlike to highly transparent by malting us e of the hydride-forming properties of Y. A strong alkaline solution i s a suitable electrolytic environment fur obtaining stable electrochro mic electrodes. The presence of a thin Pd layer covering the Y electro de is essential in providing a sufficiently high electrocatalytic acti vity for the electrochemical charge-transfer reaction. Hydrogen is irr eversibly bound in Y-dihydride and reversibly bound in Y-trihydride. T he optical changes are reversible and are induced within a narrow hydr ogen concentration range, making this typical electrode material inter esting for application in a new type of electrochromic devices.