Please use this identifier to cite or link to this item: http://prr.hec.gov.pk/jspui/handle/123456789/11418
Title: Exploring the Multifunctional Properties of BiFeO3-Based Multiferroics
Authors: Amin, Muhammad
Keywords: Physics
Issue Date: 2019
Publisher: University of the Punjab , Lahore
Abstract: Multiferroics, displaying more than one ferroic characteristics in the same phase, constitute an energetic group of materials with rich fundamental Physics and many promising applications in modern technologies. Polycrystalline fine powders of Bi0.9Sr0.1FeO3 (residue-BSFO), Bi0.9Sr0.1Fe1-xMnxO3 (BSFMO) (with x = 0, 0.05, 0.1, 0.15 and 0.2) and Bi0.9La0.1Fe1-xCrxO3 (BLFCO) (with x = 0, 0.05, 0.1, 0.15 and 0.2) are synthesized successfully at relatively low temperature by sol-gel auto combustion, using both glycine and urea as chelating agents. BSFMO samples were sintered at 550 ℃ for 3 h while BLFCO samples at 600 ℃ for 2 h. The structural, morphological, dielectric, electrical, magnetic and ferroelectric properties of the synthesized samples were explored using the corresponding characterization techniques. Rietveld's refined XRD patterns of all the prepared samples have confirmed that phase pure BFO ceramics were synthesized which exhibited distorted perovskite crystal structure (ABO3 type) having space group R3c (161). Co-doping of Sr/Mn & La/Cr at Bi/Fe sites respectively in BFO have not altered the crystal symmetry of the parent compound. FESEM images showed homogeneous microstructures with uniformly distributed and well interlinked multi-shaped grains with varying sizes, intergranular porosity and few cracks as well as a decreasing trend in grain sizes with increasing doping contents. The crystallite sizes calculated by Scherrer's formula are in the range of 9.2-15.0 nm for BSFMO and 5.8-13.7 nm for BLFCO samples. The average grain sizes shown by SEM images are in the range of 50-80 nm for BSFMO and 8-20 nm for BLFCO samples. EDX results have confirmed that all the parent and the doped elements (Bi, Fe, O, Sr, Mn, La, and Cr) are present in the synthesized samples according to their stoichiometric ratios. The dielectric behavior of all the samples have exhibited the conventional ferrite trend depicting larger values at lower frequencies which then exhibited decreasing trend with increasing frequency and finally became constant at higher frequencies. Complex impedance spectroscopy revealed the contribution of grains, grain boundaries and interfaces. The frequency dependent Nyquist and electric modulus graphs confirmed the non-Debye type relaxation. The formation of bonds between different atoms within the BSFMO compositions are identified through FTIR. Both magnetization and polarization have been observed in all the synthesized samples which have confirmed that the synthesized BFO based nanoparticles possess more than one ferroic order in the same v phase, and at the same time i.e. the samples exhibit multiferroicity. In the present work, the characteristics shown by the samples have been explained on the basis of dopant elements, their doping percentage, purity of phases, grain sizes and their microstructures. In summary, the sol-gel auto-combustion technique is suitable to synthesize phase pure BFO ceramics if the stoichiometric ratios of raw materials and the reaction parameters are controlled. The synthesized samples for the present research work are more pure, better and cost effective as compared to those which were found in literature. Almost all the prepared samples are impurity free so, the contribution of parasitic phases in improving multifunctional properties of the synthesized samples is negligible. Co-doping of Sr/Mn in Bi0.9Sr0.1Fe1-xMnxO3 and La/Cr in Bi0.9La0.1Fe1-xCrxO3 compositions have yielded improved and viable multiferroic features which would be beneficial to fabricate multifunctional devices for future technology in order to fulfill the needs of coming generations.
Gov't Doc #: 18710
URI: http://prr.hec.gov.pk/jspui/handle/123456789/11418
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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