Development of a novel (Mg0.25Co0.25Ni0.25Zn0.25)O medium entropy oxide for dielectric applications

A novel quaternary medium-entropy rock-salt oxide (Mg0.25Co0.25Ni0.25Zn0.25)O (MERO) was predicted using first-principles calculation and prepared through solid-state reaction. The first-principles study demonstrated that the mixing enthalpy and entropy values of the MERO are 2.377 kJ/mol and 0.693–1.040 R, respectively. The single-phase MERO can be obtained from 1000°C to 1200°C, demonstrating good thermal stability, whereas a completely disordered occupancy of different metal cations can be confirmed by Raman spectroscopy. The Transition Electron Microscope (TEM) analysis reveals that the MERO exhibits an FCC structure with a lattice parameter of 4.384 Å. The dielectric permittivity εr of MERO prepared at 1200°C shows relatively high values of 6.4 × 103 and 18.40 corresponding to frequencies of 100 Hz and 1 MHz at room temperature, exhibiting a potential for application in electrode materials and capacitors.