Swallow J G, Kim J J, Maloney J M, et al. Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures[J]. Nature materials, 2017, 16(7): 749-754.

ABSTRACT

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−$\delta$ (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 \textgreater0.1\% were achieved with electrical bias values \textless0.1V, 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 coupled oxide films at extreme temperatures.