Investigation of ferroelectric and dielectric properties of aluminium doped BiFeO3 thin films coated by facile nebulized spray pyrolysis route

Bismuth ferrite (BiFeO₃, BFO) plays a significant role as a ferroelectric material, yet it suffers from several drawbacks, including the presence of impurity phases, and high dielectric loss (tan δ). In this study, we report aluminium (Al)-doped BFO (BFAO) thin films with varying dopant concentrations (0–8 at%), which were successfully synthesized using the nebulizer spray pyrolysis technique. Notably, this technique provides a cost-effective and scalable route for depositing uniform, phase-pure films with precise stoichiometric control. The effect of Al incorporation on the structural, morphological, compositional, and functional properties of BiFeO₃ (BFO) was systematically investigated. The optimized 4 at% Al-doped BFO (4Al-BFO) exhibits a single-phase perovskite structure with high crystallinity and slight changes in lattice parameters. SEM reveals homogeneous, densely packed grains, and EDS confirms the uniform presence of Al within the films. XPS and Raman spectroscopy indicate modifications in Fe–O bonding, a reduction in oxygen vacancies, and subtle lattice distortions with increasing Al content. For the P–E loop, 4Al-BFO exhibits robust and switchable polarization, characterized by significant remanent polarization and moderate coercivity even at 250 kV/cm. This behavior results from Al substitution in the BFO film, which effectively mitigates leakage and defect-related losses, thereby stabilizing the ferroelectric domains. Furthermore, 4Al-BFO exhibits a higher dielectric constant (slightly above 2) compared to BFO. In addition, it maintains a consistently low and nearly constant dielectric loss across the entire frequency range, which is crucial for energy storage and capacitor applications. These results suggest that controlled Al doping is an effective strategy to tailor the multifunctional properties of BFO thin films for potential applications in non-volatile memory devices, sensors, and magnetoelectric systems.