Effect of Pr substitution on the structure, nanomechanical and multiferroic characterizations of Bi1-xPrxFeO3 polycrystalline films

Abstract

In this work, we adopt pulse laser deposition (PLD) with Nd: YAG laser to grow Bi1-xPrxFeO3 (BPFO) thin films on Pt buffered glass substrates at the reduced temperature (450 °C). We discuss their structure, microstructure, ferroelectric, magnetic, and nanomechanical, properties via x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ferroelectric test system, vibrating sample magnetometer (VSM), and nanoindenter, respectively. BiFeO3 (BFO) thin films consist of a major perovskite phase and minor impurity (Bi2Fe4O9) phase. An impurity phase is suppressed by Pr substitution. Besides, a structure transformation from rhombohedral to orthorhombic (R-O) phase was observed for higher Pr content near x = 0.15. The surface morphology shows a gradual reduction in the crystallite size and roughness with increasing Pr content. The hardness in the range of 3.7–8.3 GPa found for BPFO films was dependent on crystal structure and grain size. The remanent polarizations (2Pr) in the range of 25–124 μC/cm2, and coercive field (Ec) in the range of 309–590 kV/cm points out good ferroelectric properties in studied BPFO films. The enhancement of the ferroelectric properties is possibly resulted from the suppression of the impurity phase and the diminution of the leakage due to flattened interface and refined microstructure with small grain sizes of 60–200 nm. Improved magnetic properties with the saturation magnetization of 3.6–18.2 emu/cm3 and coercivity of 302–520 Oe by Pr substitution resulted from magnetic moment of Pr3+ ion and suppressed spiral spin configuration structure. The mechanisms of leakage behavior and nanomechanical characterizations as functions of Pr content are also studied.