The study presents a thermodynamic model and experimental evidence demonstrating that entropy, rather than enthalpy, dominates the stability of mixed oxides. By engineering configurational disorder into a single sublattice with multiple distinct cations, the researchers show that entropy stabilizes crystalline matter, enabling reversible solid-state transformations between multiphase and single-phase states. The findings validate the hypothesis that deliberate configurational disorder can be used to discover new phases of crystalline matter and enable property engineering. The research focuses on a five-component oxide formulation, E1, composed of equimolar mixtures of MgO, CoO, NiO, CuO, and ZnO. Experiments show that at high temperatures, the oxide undergoes a reversible transformation to a single-phase rocksalt structure, with cation distributions being random and homogeneous. The study also demonstrates that entropy-driven transitions are endothermic, requiring external heat input, and that the transition temperature depends on composition, with higher entropy leading to lower transition temperatures. The researchers used X-ray diffraction, differential scanning calorimetry, and scanning transmission electron microscopy to analyze the phase transitions and cation distributions. These techniques confirmed that the cations are uniformly dispersed and that the oxide is truly entropy-stabilized. The study also shows that configurational entropy is particularly effective in ionic compounds, and that the entropy-stabilized oxides represent a new class of materials with unique thermodynamic and structural properties. The findings have implications for materials science, as they provide a new strategy for discovering and engineering new materials with desired properties. The study highlights the importance of entropy in oxide systems and suggests that similar phenomena may occur in non-metallic systems. The research also underscores the potential of high-throughput methods and computational approaches in materials discovery, and the need for further theoretical exploration of entropy-driven phase transitions.The study presents a thermodynamic model and experimental evidence demonstrating that entropy, rather than enthalpy, dominates the stability of mixed oxides. By engineering configurational disorder into a single sublattice with multiple distinct cations, the researchers show that entropy stabilizes crystalline matter, enabling reversible solid-state transformations between multiphase and single-phase states. The findings validate the hypothesis that deliberate configurational disorder can be used to discover new phases of crystalline matter and enable property engineering. The research focuses on a five-component oxide formulation, E1, composed of equimolar mixtures of MgO, CoO, NiO, CuO, and ZnO. Experiments show that at high temperatures, the oxide undergoes a reversible transformation to a single-phase rocksalt structure, with cation distributions being random and homogeneous. The study also demonstrates that entropy-driven transitions are endothermic, requiring external heat input, and that the transition temperature depends on composition, with higher entropy leading to lower transition temperatures. The researchers used X-ray diffraction, differential scanning calorimetry, and scanning transmission electron microscopy to analyze the phase transitions and cation distributions. These techniques confirmed that the cations are uniformly dispersed and that the oxide is truly entropy-stabilized. The study also shows that configurational entropy is particularly effective in ionic compounds, and that the entropy-stabilized oxides represent a new class of materials with unique thermodynamic and structural properties. The findings have implications for materials science, as they provide a new strategy for discovering and engineering new materials with desired properties. The study highlights the importance of entropy in oxide systems and suggests that similar phenomena may occur in non-metallic systems. The research also underscores the potential of high-throughput methods and computational approaches in materials discovery, and the need for further theoretical exploration of entropy-driven phase transitions.