High-Entropy Oxides in the Mullite-Type Structure

Andrea Kirsch*, Espen Drath Bøjesen, Niels Lefeld, Rasmus Larsen, Jette Katja Mathiesen, Susanne Linn Skjærvø, Rebecca Katharina Pittkowski, Denis Sheptyakov, Kirsten M.Ø. Jensen*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


High-entropy materials (HEMs) represent a new class of solid solutions containing at least five different elements. Their compositional diversity makes them promising as platforms for the development of functional materials. We synthesized new HEMs in a mullite-type structure and present five compounds, i.e., Bi2(Al0.25Ga0.25Fe0.25Mn0.25)4O9 and A2Mn4O10 with variations of A = Nd, Sm, Y, Er, Eu, Ce, and Bi, demonstrating the vast accessible composition space. By combining scattering, microscopy, and spectroscopy techniques, we show that our materials are mixed solid solutions. Remarkably, when following their crystallization in situ using X-ray diffraction and X-ray absorption spectroscopy, we find that the HEMs form through a metastable amorphous phase without the formation of any crystalline intermediates. We expect that our synthesis is excellently suited to synthesizing diverse HEMs and therefore will have a significant impact on their future exploration.

Original languageEnglish
JournalChemistry of Materials
Pages (from-to)8664-8674
Number of pages11
Publication statusPublished - Oct 2023


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