Designing nanostructure exsolution-self-assembly in a complex concentrated oxide

Complex concentrated oxides (CCOs) are an emerging material class that includes high-entropy and entropy-stabilized oxides whose properties stem from disorder-induced electronic structure and chemistry caused by stabilizing solid solutions of >5 cations. Integrating CCOs into composites will expand material design beyond the single-phase paradigm. We demonstrate tunable CCO-derived nanostructures by a simple method: exsolution-self-assembly (ESA), a one-step approach to direct the evolution of nanoparticles and nanorods in nanocomposites. We have developed a fundamental understanding of driving forces and formation mechanisms in CCOs using atomic-scale probes, which reveal that ESA can be directed using Ellingham's model of cation reducibility in a model CCO perovskite LaFe0.7Ni0.1Co0.1Pd0.05Ru0.05O3-delta. This approach enables tailored growth of multielement nanorod and nanoparticle composite structures whose formation is correlated with electronic conductivity that exceeds 0.1 S/cm at room temperature. Given the vast combinatorial space of CCOs, ESA is expected to be highly extensible via the integration of various compositions and crystal structures.