Physical properties of Pr_1-xBi_xFeO₃ prepared by microwave-assisted hydrothermal method

Full text: Multiferroic materials have been studying due to their important physical properties. Among these materials, the BiFeO₃ (BFO) compounds is one of the few known materials that present this effect and is a very promising material to apply in multifunctional devices. Although, the presence of Bi in such compounds causes instability and creates impurities that affect their electric conductivity. In such case, this effect can be reduced by substitution of Bi by others elements as, for example, rare earths. In this context, the aim of this work is to synthesize multiferroic compounds of Pr_1-xBi_xFeO₃ by microwave-assisted hydrothermal method. To investigate the best synthesis parameters, compounds of BFO were obtained by different temperatures and times. The structural properties were performed by X-ray powder diffraction (XRD) in order to investigate the phase by using a Bruker D8 Focus X-ray Diffractometer. From these results, we chose the best conditions to prepare all compounds by this methodology. Then, these results revealed that samples crystallize in a rhombohedrally-distorted perovskite structure (space group symmetry R3c) with some impurities as Bi₂Fe₄O₉ and Bi₁₂FeO₂₀. XRD data indicates that the presence of Pr in the structure of BFO reduces these impurities. Also, images of scanning electron microscopy (SEM) have been obtained to examine the morphological properties by using the SEM of JEOL (JSM-6701F). The SEM micrographs revealed that samples present square shaped grains with sizes smaller than 100 nm. The magnetic properties were characterized through magnetization measurements as a function of applied magnetic field and temperature. Such characterizations were carried out in a physical properties measurements system (PPMS) of Quantum Design. In addition, electrical properties have been characterizing through impedance spectroscopy in a Solartron system. The effect of the substitution of Bi for Pr in BFO seems to enhance electric and magnetic properties. (author)