Chemistry Seminar – Dr. Yingge Du

About the event

Speaker: Yingge Du, Ph.D., Physical Sciences Division, Pacific Northwest National Laboratory

Host: Dr. Xiaofeng Guo

Title: When High-Entropy Meets Epitaxy: Emergent Phenomena in Multi-Component Complex Oxide Thin Films

Abstract: In this talk, I will begin with an overview of current research directions in complex oxide thin films at PNNL, and then narrow the focus to a particularly intriguing materials class: high-entropy perovskite oxides (HEOs) with the ABO3 structure. Perovskite oxides offer a versatile platform for exploring emergent phenomena as compositions evolve from conventional multicomponent systems toward the high-entropy limit.

A central theme of this work is the delicate balance between the chemical disorder intrinsic to high-entropy design (using La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 as a model system),and the structural order imposed by epitaxial growth. Recent advances in epitaxial synthesis and characterization have made it possible to harness aliovalent doping, epitaxial strain, and controlled chemical potentials to stabilize unconventional valence states, vacancy-ordered lattices, and metastable phases that are inaccessible through bulk synthesis. Cr provides a compelling model system for investigating this redox adaptability, enabling access to non-equilibrium configurations in both single-cation and multi-cation perovskites. When extended to high-entropy perovskites, this interplay becomes even more complex, as nanoscale compositional fluctuations and Cr-rich motifs emerge from competition among multiple cation species. By coupling entropic disorder with epitaxial constraint, this work reveals new pathways to engineer metastability, tune redox flexibility, and ultimately unlock novel functionalities in complex oxide thin films.