Critical role of cationic local stresses on the stabilization of entropy-stabilized transition metal oxides

LK Bhaskar and V Nallathambi and R Kumar, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 103, 3416-3424 (2020).

DOI: 10.1111/jace.17029

Entropy-stabilized transition metal oxides (MgNiCoCuZnO) (ESO) in recent years have received considerable attention owing to their unique functional properties. Solution combustion and solid state syntheses resulted in crystallites varying from 5-15 nm to 3-5 mu m respectively. Phase stability studies showed that all the systems containing Cu2+ ions in the ESO lattice segregated upon slow cooling in the furnace. It was only when ESO was quenched in air from 1000 degrees C the lattice stabilized to a single phase. Experiments concomitant with molecular dynamics (MD) simulations demonstrated that the local stress fields around the cations played a critical role in stabilizing the single phase. The local stress fields are a result of Jahn-Teller distortion induced by the Cu2+ ions in the lattice. It is clearly established that in the absence of the minimization of the local stress fields around the Cu2+ ions, segregation leading to the formation of a multi-phase material is imminent for this particular composition.

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