Optimizing physical properties of BiFe1-xMnxO3 perovskite thin films via a low-temperature sol-gel method

Abstract

Multiferroic materials have recently attracted great attention for possible use in photovoltaic and photocatalytic devices. In this study, pure-phase BiFe1-xMnxO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) thin films were deposited on glass substrates via low-temperature sol-gel assisted spin coating procedure. We found that the thin films undergo a rhombohedral to cubic structural transition. From FESEM images, it was observed that different amount of Mn affects the surface morphology and grain size of the studied samples. For all samples, the absorption coefficient was in the range of 105 cm−1, and the refractive index and extinction coefficient of samples were about 1.15–1.50 and 0.2–0.9, respectively. BiFe0.8Mn0.2O3 thin film has the lowest bandgap energy due to the highest absorption coefficient at the wavelengths of 400–1100 nm denoted by its lowest transmittance. Structural and magnetic results show the substitution of low-spin smaller Mn ions for high-spin larger Fe ions. The best photocatalytic activity was observed for BiFe0.8Mn0.2O3 thin film with a removal efficiency of 78.83% in the photodegradation of methylene blue.