Researchers at Penn State University have developed seven novel high-entropy oxides by reducing oxygen levels during synthesis, stabilizing metals like iron and manganese that typically destabilize. This breakthrough, published in Nature Communications, offers a framework for designing advanced ceramics for energy and electronics applications. Machine learning accelerated the discovery of promising compositions.
Materials scientists at Penn State achieved a significant advance by synthesizing seven previously unknown high-entropy oxides, or HEOs, which incorporate five or more metals. These ceramics hold potential for energy storage, electronic devices, and protective coatings. The key innovation involved lowering oxygen in the synthesis environment to enable stable rock-salt structures.
The process began with an initial experiment on a composition labeled J52, containing magnesium, cobalt, nickel, manganese, and iron. By adjusting oxygen levels in a tube furnace, lead researcher Saeed Almishal stabilized iron and manganese in their 2+ oxidation state, preventing them from binding excess oxygen as they would in normal atmospheres. "By carefully removing oxygen from the atmosphere of the tube furnace during synthesis, we stabilized two metals, iron and manganese, into the ceramics that would not otherwise stabilize in the ambient atmosphere," Almishal explained.
Building on this, Almishal employed machine learning to screen thousands of formulations, identifying six more viable metal combinations. Undergraduate and graduate students assisted in fabricating and characterizing solid ceramic pellets for all seven HEOs. "In a single step, we stabilized all seven compositions that are possible given our current framework," Almishal noted, crediting thermodynamic principles for the straightforward solution.
To confirm the materials' stability, the team partnered with Virginia Tech researchers, who used X-ray absorption imaging to verify the oxidation states. The work, supported by Penn State's Center for Nanoscale Science, underscores oxygen's critical role in ceramic formation. Future efforts will test the HEOs' magnetic properties and apply the method to other challenging materials.
Undergraduate contributor Matthew Furst presented the findings at the American Ceramic Society's 2025 meeting in Columbus, Ohio, highlighting student involvement. The study, already widely accessed online, provides a versatile approach for complex oxide synthesis.