Defect Engineering Through Ni/Co/Fe‐Doping in LaMnO ₃ Perovskite Oxides for Enhanced Dielectric and Electrochemical Properties

Transition metal substitution is an effective strategy for tuning the versatile characteristics of perovskite oxides. Here, we demonstrate that transition metals like Ni, Co, and Fe doping (3%) in lanthanum manganite (LaMnO ₃ ) causes oxygen vacancies, which play a vital part in improving the material's optical, dielectric, and electrochemical performance. By causing charge imbalance and lattice distortions, dopant insertion encourages the creation of oxygen vacancies, which alter the electronic structure and carrier transport. Among the synthesized samples, Fe‐doped LaMnO ₃ exhibited the highest dielectric constant (5823 at 100 kHz) along with reduced dielectric loss, indicating improved dielectric performance. The doped samples showed variations in magnetic susceptibility, arising from modifications in the Mn–O–Mn exchange interactions caused by dopant incorporation, while maintaining paramagnetic behavior at room temperature. With an areal capacitance of 60.36 mF cm ⁻² and almost 100% retention over 10,000 cycles, the Fe‐doped perovskite oxide exhibits outstanding electrochemical energy‐storage properties. An LCD was successfully powered by an asymmetric supercapacitor device fabricated with this electrode material, demonstrating its practical application. These results indicate that transition metal doping effectively tunes the functional properties of LaMnO ₃ , making it a promising candidate for advanced electronics and energy storage technologies.