Multiferroic properties of La-doped BiFeO3 thin films on highly ordered pyrolytic graphite single-crystal substrates using PLD for energy storage applications

La-doped Bi_1.2FeO₃ (BFO) thin films deposited on highly ordered pyrolytic graphite (HOPG) substrates were synthesized using pulsed laser deposition method (PLD). The impact of the lanthanum (La) doping on the leakage current, ferroelectric, magnetic, and fatigue properties of the thin films was investigated. This study explores the energy storage and multiferroic properties, focusing on the influence of incorporated La concentrations. Preferentially, (111)-oriented polycrystalline BFO thin films, particularly doped with 10 mol.% La, demonstrated superior crystallinity and exceptional ferroelectric properties. As La concentration increased, BFO thin films exhibited improved leakage current characteristics and enhanced magnetic properties. The remanent polarization of BFO thin film was approximately 23.9 μC/cm² without La doping. However, as La doping concentration increased to 5 and 10 mol.%, it significantly improved to approximately 32.6 and 48.4 μC/cm²; respectively. Notably, BFO thin films doped with approximately 15 mol.% La achieved a maximum energy density of around 70.6 J/cm³, coupled with an energy storage efficiency of approximately 68.2% and a loss energy density of about 32.9 J/cm³. This performance enhancement is attributed to the improved ferroelectric properties and reduced leakage current enabled by La doping. Thus, the deposition of polycrystalline BFO thin films on HOPG substrates and the optimization of their energy storage properties through La doping provide promising advancements for energy storage technologies.