Bi_0.9Ho_0.1FeO₃/TiO₂ Composite Thin Films: Synthesis and Study of Optical, Electrical and Magnetic Properties

A visible light active Bi_0.9Ho_0.1FeO₃ nanoparticles/TiO₂ composite thin films with different mol.% of Bi_0.9Ho_0.1FeO₃ were successfully prepared via non-aqueous sol-gel method. The incorporation of 5, 10 and 20 mol.% Bi_0.9Ho_0.1FeO₃ nanoparticles in the precursor solution of TiO₂ brings modifications in the functional properties of the composite thin films. XPS analysis indicates that interdiffusion of Fe³⁺, Ho³⁺, Bi³⁺/Ti⁴⁺ ions through the interfaces between Bi_0.9Ho_0.1FeO₃ nanoparticles and TiO₂ matrix reduces the concentration of Ti³⁺ ions. X-ray diffraction analysis affirms that TiO₂ and Bi_0.9Ho_0.1FeO₃ retain anatase and orthorhombic phase respectively in composite films. The composite thin film containing 20 mol.% Bi_0.9Ho_0.1FeO₃ nanoparticles exhibits the most prominent absorption phenomenon in visible region and has significantly reduced indirect band gap of 2.46 eV compared to that of pure TiO₂ (3.4 eV). Hall effect measurements confirm that the resistivity of composite film increases by ∼2.33 orders of magnitude and its carrier concentration decreases by 1.8 orders of magnitude at 5 mol.% Bi_0.9Ho_0.1FeO₃ nanoparticles addition compared to those of pure TiO₂ film. Moreover, the pure film exhibits diamagnetism, whereas the composite films have both large ferromagnetic and small diamagnetic components. The findings in this research justify that the composite film can be a potential candidate for making improved photocatalyst, resistors and spintronic devices.