Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties
Abstract
Nanostructured functional oxides play an important role in enabling clean energy technologies and novel memory and processor devices. Using thin‐film La 0.6 Sr 0.4 FeO 3 (LSF) as a model system, the novel utility of exsolution in fabricating self‐assembled metal oxide nanocomposites with tunable functionalities is shown. Exsolution triggers the formation of metallic iron (Fe 0 ) nanoparticles, Ruddlesden–Popper domains, and nm‐scale percolated Fe‐deficient channels in LSF. Combining multimodal characterization with numerical modeling, the chemical, magnetic, and electrical properties of the exsolution‐synthesized nanocomposite at different stages of Fe 0 exsolution as well as during redox cycling are assessed. After exsolution, the electronic conductivity of the nanocomposite LSF increased by more than two orders of magnitude. Based on numerical analysis representing all the constituents, it is expected that this increase in conductivity originates mainly from the Fe‐deficient percolating channels formed during exsolution. Moreover, the exsolved nanocomposite is redox‐active even at moderate temperatures. Such redox capabilities can enable dynamic control of the nanocomposite functionality by tailoring the oxygen non‐stoichiometry. This concept is demonstrated with a continuous modulation of magnetization between 0 and 110 emu cm −3 . These findings point out that exsolution may serve as a platform for scalable fabrication of complex metal oxide nanocomposites for electrochemical and electronic applications.
The authors would like to thank the Exelon Corporation and the MIT Energy Initiative Seed Fund Program for supporting the work presented in this paper. This research used the synchrotron radiation facilities at the National Synchrotron Light Source II (IOS/23‐ID‐2 beamline), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE‐SC0012704; and the Advanced Light Source which was supported by the DOE Office of Basic Energy Sciences under Contract No. DE‐AC02‐05CH11231. For STEM‐EDS characterization work, the authors acknowledge the use of facilities and instrumentation at the UC Irvine Materials Research Institute (IMRI), which is supported in part by the National Science Foundation through the UC Irvine Materials Research Science and Engineering Center (DMR‐2011967). J.W. thanks Dimitrios Fraggedakis (MIT) for the helpful discussions on the Hashin–Shtrikman bounds. J.W. thanks Andreas Nenning (TU Wien) for the assistance on the Van der Pauw measurements. W.J.B. acknowledges UCI new faculty start‐up funding. K.S. acknowledges support from US Department of Education Graduate Assistance in Areas of National Need (GAANN) Fellowship. C.R. and S.N. acknowledge support from NSF DMR 1419807.
