On the homogeneity of high entropy oxides: An investigation at the atomic scale

Homogeneous distribution of the constituent elements at the atomic scale in high entropy oxides (HEOs) was demonstrated for the first time by atom probe tomography (APT). Three different single-phase HEOs having rocksalt, fluorite, and perovskite type crystal structures were synthesized using nebulized spray pyrolysis process. The as-synthesized powders were compacted into pellets under high pressure of 6 GPa. Both as-synthesized and compacted powders were investigated by X-ray diffraction and transmission electron microscopy. APT results showed that the constituent cations in all three HEO systems were homogenously distributed with no significant segregation or concentration fluctuation even at the atomic scale.