Electro‐chemomechanical Contribution to Mechanical Actuation in Gd‐Doped Ceria Membranes

다국어 초록 (Multilingual Abstract)

Gd‐doped ceria (CGO), one of the most extensively studied oxygen ion conductors, is a low dielectric constant/low mechanical compliance material exhibiting large nonclassical electrostriction. The electromechanical response of the micro‐electromechanical devices with CGO films as an active material described previously can not be attributed exclusively to electrostriction. Here it is shown that, below 1 Hz, in addition to electrostriction (second‐harmonic response), there is a strong contribution of the electro‐chemomechanical effect (ECM, first harmonic response). ECM is the change in mechanical dimensions of ionic and mixed ionic‐electronic conductors as a result of a change in chemical composition induced by an electric field. In batteries, the presence of ECM is highly detrimental. In ceria at room temperature, it was considered to be negligible because of slow oxygen diffusion. This work demonstrates ECM actuation at ambient temperature and moderate electric field (<5 V µm−1). ECM‐induced strain is attributed to reversible oxidation/ reduction of TiO2 layers at the Ti‐CGO interface. At 25 °C, the ECM bending strain is 1.2 × 10−6, increasing exponentially with temperature. These data suggest that with a proper choice of materials, ECM‐type response can be a viable mechanism for mechanical actuation at ambient and also at slightly elevated temperatures.
Electromechanical response of Al/Ti/Ce0.8Gd0.2O1.9/Ti/Al structure consists of two contributions: electrostriction at the second harmonic (top panel), which involves in‐plane expansion, and the electro‐chemomechanical effect at the first harmonic (bottom panel), which originates from oxidation/reduction of Ti at the Ce0.8Gd0.2O1.9/Ti interface.