STUDY OF STRUCTURAL, DIELECTRIC AND MULTIFERROIC PROPERTY OF SUBSTITUTED BISMUTH FERRITE

Abstract

Chapter 1 It gives the overview of Multiferroics materials, its type and reason for simultaneous occurrence of different ferroic order, and the conditions required for a system to have ferroelectricity and the dependence of ferroelectric hysteresis loop on temperature. An introduction to perovskite structure has also been given in this chapter. Chapter 2 Bulk samples of Bio.8Ca0.2Fe1_XCrXO3 (x= 0.0, 0.3, 0.5 and 0.7) were synthesized using solid state reaction method. Structural characterization of the samples has been done by using X-ray diffraction (XRD), Field emission-Scanning electron microscope (FE-SEM), Energy dispersive analysis of x-ray spectroscopy (EDAX) A brief description of these techniques has been made in this particular chapter. Chapter 3 Chapter 3 explored the influence of sintering temperature on the structural, dielectric and ferroelectric properties of bulk BiFeO3 . Single-phase polycrystalline pure BFO and BiO.75Ca0.52 Fe03 samples have been prepared using solid state reaction technique. For doped sample, Ca substitution in BiFeO3 at Bi-site does not change its structure. But, both the lattice parameters 'a' and `c ' are found to decrease systematically with the incorporation of Ca. A diffused dielectric anomaly has been found in the temperature dependent dielectric data. Due to incorporation of Ca, magnetic disorder has been introduced into the system. The ferroelectric loops of these samples are observed at room temperature owing to high resistivity and suppression of the charged defects. The enhanced magnetic properties were attributed to the suppression of the space spin-modulated magnetic structure in BCFO ceramics. Chapter 4 The effect of Cr doping in the BFO compound on its structural, magnetic and multiferroic behavior have been studied. The rhombohedral structure of BFO is not altered and the lattice parameters decrease with the Cr content. It is found that the lattice parameters a and c and the Fe —0 (1) bond lengths vary decreasingly as x values rise from 0.0 to 0.07. The substitution Cr for Fe can enhance the magnetization due to the strong ferromagnetic interaction between Fe3 +and Cr3 +and the structure distortion with introduction of Cr. BiFel—xCrxO3 simultaneously shows ferroelectricity at room temperature. The synthesis of the pure BiO.75CaO.25Fe1—xCrxO3 provides not only the opportunity to investigate the role of Cr in BFCO compounds but also shows the possibility for other nonequilibrium method to synthesize the BFCO compounds with high Cr content. Chapter 5 Future prospects have been discussed in this chapter