A recent study has highlighted how the methods used to synthesize high entropy oxides can significantly influence their structural and functional characteristics, which are vital for their applications in common electronic devices. The findings were published this week in the Journal of the American Chemical Society.
The findings of this new study reveal for the first time the substantial impact different synthesis methods have on the structural and functional traits of high entropy oxides, a group of materials utilized in everyday electronics. This research appeared in this week’s edition of the Journal of the American Chemical Society.
“The specific material we examined is a high entropy oxide featuring a spinel crystal structure, which consists of a blend of five different transition metal oxides. The growing interest in these materials stems from their remarkable electrochemical properties,” explained Dr. Alannah Hallas, a materials scientist at the University of British Columbia’s Blusson Quantum Matter Institute and the Department of Physics and Astronomy.
“These high entropy systems are incredibly promising due to their considerable chemical versatility. When creating these materials, we have numerous variables to manipulate, which opens up endless possibilities for how we can design them.”
The researchers crafted identical samples using five distinct synthesis techniques: solid state, high pressure, hydrothermal, molten salt, and combustion syntheses. Each method differs in how the material is heated, the cooling rates back to room temperature, and the various chemical environments in which the heating takes place.
“Our findings clearly indicate that the synthesis method is crucial. Although the overall structure remains consistent, we noted substantial differences in the local structures and microstructures of the samples, with combustion synthesis yielding the most uniform samples,” stated Mario Ulises González-Rivas, the lead author of the study and a skilled researcher in synthesizing samples in Hallas’s group during his PhD.
Each synthesis method employs a unique driving mechanism to form the material, González-Rivas explained. In the solid-state approach, metal oxides are combined and heated together, akin to baking a cake. The high-pressure technique applies additional pressure while heating, affecting the material’s formation. The hydrothermal method simulates the natural formation of minerals in the Earth’s core by heating metal salts in water within a pressurized environment, creating a flow that fosters crystal growth. The molten salt method involves melted metal salts that become a viscous liquid, allowing crystals to precipitate as they cool. Finally, the combustion method requires dissolving metal salts in water, creating a gel that ignites and quickly produces the desired material through a rapid combustion reaction.
“Certain materials created through these processes show great promise for addressing energy challenges. The structural variations highlighted in our study significantly influence the technological application of these materials within energy systems,” González-Rivas noted. “Our results offer a new approach for optimizing the use of these materials in practical applications.”
This research was a collaborative effort involving Hallas’s team at UBC Blusson QMI, Dr. Robert Green, a UBC Blusson QMI Affiliate Investigator from the University of Saskatchewan, and Dr. Hidenori Takagi from the Max Planck Institute for Solid State Research.
