Structural modulation, oriented growth of rock salt, and spinel in (Co(Cr/Mg)FeMnNi) multicomponent oxide and derivatives

Abstract Phases, interfaces, microstructure, and stabilization mechanism in multicomponent (Co(Cr/Mg)FeMnNi)‐oxide along with its binary, ternary, and quaternary derivatives, synthesized through solid‐state route, have been studied by X‐ray diffraction and transmission electron microscopy. Formation of single‐phase spinel in multicomponent (CoFeMgMnNi)‐oxide after sintering at 1473 K for 10 h is being reported with preferential growth of rock salt phase upon longer holding time. Oriented growth of spinel with rock salt and formation of coherent/semi‐coherent interface structure helps in minimizing the interface strain. Equimolar ternary derivative, (CoMgNi)‐oxide, after sintering at 1473 K for 10 h forms a rock salt phase along with a minor volume fraction of spinel phase. Ternary (CoMgNi)‐oxide and multicomponent (CoFeMgMnNi)‐oxide, upon prolonged sintering or aging, develop structural modulation with/without chemical partitioning that is evident from the electron diffraction patterns through spot splitting, intensity modulation, and arcing. Single‐phase spinel forming (CoCrFeMnNi)‐multicomponent oxide develops structurally modulated microstructure upon sintering and quenching, which is being observed for the first time. Stabilization of the multicomponent oxides is explained as a trade‐off between the high configurational entropy due to the presence of multiple cations in the cation sublattice and the minimization of strain energy in the crystal of the multicomponent oxide.