Enhanced ferroelectric properties in La-doped BiFeO 3 films by the sol-gel method

High-quality spin-coated Bi 1-x La x FeO 3 (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) films were successfully produced on fluorine-doped tin oxide (FTO)/glass substrates using a sol-gel approach. The effects of La-doping on the structure, surface morphology, and ferroelectric properties of BFO films were thoroughly investigated. Doping causes structural alterations, which are detected using XRD and Raman spectrum analyses. SEM pictures demonstrate that Bi 1-x La x FeO 3 thin films with x = 0.02 have homogeneous fine grains and a greater density, which facilitate the development of ferroelectric characteristics. The XPS study revealed that the incorporation of La 3+ significantly reduced the content of Fe 2+ and oxygen vacancies, resulting in a massive residual scheme value (2 P r = 280.4 µC/cm 2 ) and an extremely low leakage current density ( J = 1.1 × 10 –6 A/cm 2 ). Similarly, the dielectric constant and dielectric loss were significantly improved. Furthermore, UV-vis spectroscopy was used to detect the band gap of the BFO samples, which revealed that the La-doped sample had a smaller band gap than pure BFO. The fundamental principles based on oxygen radical concentration have been described, providing a unique platform to develop improved ferroelectric materials with broad applications. Graphical abstract The Bi 1-x La x FeO 3 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) films: (a) Relationship between the frequency-dielectric constant; (b) Relationship between the frequency-dielectric loss; (c) Leakage current density curves of the BLFO thin films.; (d) Log J –log E characteristics of the BLFO thin films. It can be seen from the figures that La doping effectively improved the dielectric properties and the leakage characteristics of the films.