Enhanced magnetic, dielectric and photoconductive properties of Zr doped BiFeO3 nanostructures

Abstract

Lead-free ferroelectric BiFe1-xZrxO3 (x = 0.0, 0.015, and 0.025) thin films with varying concentrations of Zr4+ ions were fabricated using nanoparticles synthesized by the hydrothermal method. The X-ray diffraction analysis reveals that the as-synthesized pure and Zr-doped nanoparticles possess distorted rhombohedral structures. The diffraction peak at 32° shifts to the lower angle with increase in Zr content. For higher concentration of Zr4+ ions (2.5% Zr-doped BFO), the impure phase Bi2Fe4O9 evolved and increased the leakage current. Both the SEM and TEM images of pure and doped samples exhibit irregularly shaped clusters of agglomerated nanocrystallites. The SAED pattern of the samples confirms that the samples are highly crystalline and the diffracted rings matched with the lattice planes of single-phase pristine bismuth ferrite (BFO). The Raman E modes of 1.5% Zr-doped BFO nanoparticles are relatively higher in intensity as compared to other samples and exhibited a very weak dependence of dielectric constant on frequency. On comparing, a 1.5% Zr-doped BFO sample showed lowest dielectric constant (∼79) at 1 kHz due to the filling of oxygen vacancies by Zr4+ ions and hence displayed a significant photocurrent of ∼3.10 μA at 5 V. However, for 2.5% Zr dopant concentration, the dielectric constant is quite high at 1 kHz due to the reduction of Fe3+ ion and increased oxygen vacancies; and consequently showed very feeble photocurrent of ∼9.00 nA at 5 V. Furthermore, higher ferromagnetic ordering between Fe3+ and Zr4+ in 2.5% Zr-doped BFO nanostructure has resulted in larger remnant magnetization of 0.585 emu/g. The present study confirms that the optimum concentration of Zr ions substituted at the Fe-site of BiFeO3 reduces the leakage current and improves its photoconductive properties. Besides, the aging problem of BFO nanostructures caused by oxygen vacancies due to the reorientation of dipoles can be significantly reduced through Zr doping. Hence, the enhanced temperature-dependent photo sensing properties of doped BFO nanostructures are more suitable to serve as an active layer in self-powered photodetector systems.