A detailed investigation of lanthanum substituted bismuth ferrite for enhanced structural, optical, dielectric, magnetic and ferroelectric properties

Abstract

Lanthanum substituted bismuth ferrites (Bi1-xLaxFeO3) (x = 0.0, 0.015, 0.03, 0.045 and 0.06) was successfully synthesized by using co-precipitation method. Rare earth substitution in bismuth ferrites enhanced the leakage current which is one of the problems faced by the pure bismuth ferrites. The prepared samples were investigated by XRD, SEM, EDX, TEM, FT-IR, UV–vis spectroscopy, BET, LCR for dielectric measurements, VSM for magnetic properties and ferroelectric for electric polarization. XRD pattern showed that the structure of bismuth ferrite was rhombohedral distorted perovskite structure of space group R3c and average crystallite size was determined to increase (19 nm to 35 nm) with increase in lanthanum concentration. Morphology of SEM images was found to be spherical shape. TEM shows average particle size increases from 35 nm to 50 nm. Metal-oxide bonds at 440 cm−1 and 539 cm−1 in IR spectra confirmed the perovskite structure of bismuth ferrites. UV–visible spectroscopy revealed that energy band gap decreased by increasing the Lanthanum concentration. BET shows the surface area increased from 4.79 m2/g to 9.03 m2/g. Dielectric constant increases by increasing the lanthanum concentration. AC conductivity showed maximum value at higher frequency nearly equal to 11 Ω cm−1. Electric modulus gradually increased by increasing frequency which was equal to 4.2 k Ω. Magnetic susceptibility increased by increasing the concentration and maximum value 0.008 cm3/g was observed for (x = 0.06). Magnetization (Ms), remanence (Mr), polarization (Pr) increased whereas coercivity decreased with increasing lanthanum substitution. Such properties make these materials as potential candidates for microwave devices and electromagnetic shielding application.