Choosing the metal oxide for an electro-chemo-mechanical actuator working body

The term “electro-chemo-mechanical (ECM) effect” describes mechanical deformation driven by an electrochemical reaction. Recently, an all-solid-state ECM device operating at room temperature was demonstrated. The device comprised a 20 mol% Gd-doped ceria (20GDC) self-supported electrolyte membrane placed between two mixed ionic/electronic conducting (MIEC) working bodies (WBs) constructed with TiO_x/20GDC nanocomposites. Actuation derived from volume change occurring upon oxidation/reduction of the WB. This raised the question of whether or not metal oxides other than TiO_x could be valuable components in MIEC nanocomposites functioning as WBs in ECM actuation. Here we examine the microstructure, crystal phase, oxidation state, chemical composition and ECM functionality of V-, Nb-, Mo-, Cu- and Ag-oxide/20GDC composite WBs prepared by co-sputtering. Of these, only the V-based composite was shown to be suitable for ECM actuation. According to X-ray absorption spectroscopy, the composition of the nanocomposite corresponds to VO_x/20GDC. Electrical characterization suggests that the formation of several coexisting VO_x nano-oxide phases is responsible for the longer response times as compared to TiO_x/20GDC WBs. ECM actuation demonstrated in the V-based system does indicate that composite WB based ECM is not unique to Ti and that this type of actuation constitutes a significant contribution to development of microelectromechanical systems.