Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures
Jessica G. Swallow1,2, Jae Jin Kim1,2, John M. Maloney1, Di Chen1,2, James F. Smith3, Sean R. Bishop1,2, Harry L. Tuller1,2 and Krystyn J. Van Vliet1,2*
Actuator operation in increasingly extreme and remote conditions requires materials that reliably sense and actuate at elevated temperatures, and over a range of gas environments. Design of such materials will rely on high-temperature, high- resolution approaches for characterizing material actuation in situ. Here, we demonstrate a novel type of high-temperature, low-voltage electromechanical oxide actuator based on the model material Prx Ce1−x O2−δ (PCO). Chemical strain and interfacial stress resulted from electrochemically pumping oxygen into or out of PCO films, leading to measurable film volume changes due to chemical expansion. At 650 ◦ C, nanometre-scale displacement and strain of >0.1% were achieved with electrical bias values <0.1 V, low compared to piezoelectrically driven actuators, with strain amplified fivefold by stress-induced structural deflection. This operando measurement of films ‘breathing’ at second-scale temporal resolution also enabled detailed identification of the controlling kinetics of this response, and can be extended to other electrochemomechanically detailed identification of the controlling kinet coupled oxide films at extreme temperatures.