الفهرس 
Nanotechnology and NanomaterialsOnly 14 pages are availabe for public view
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Abstract
The asymmetric orthorhombic structure of barium monoferrite (BaFe2O4), a member of MFe2O4 spinel ferrites, provides distinctive and interesting structural, magnetic and electrical properties that have been rarely explored when compared to the tremendous articles concerning the spinel ferrites of cubic-type structure. In the present thesis, structural, magnetic and electrical properties of cobalt-substituted barium monoferrite prepared by solgel autocombustion method have been investigated. Both Ba1-xCoxFe2O4 and BaCoxFe2-xO4 systems with heat treatments at different sintering temperatures were thoroughly analyzed. Singlephase orthorhombic structure has been observed for x = 0.0 for all sintering temperatures. Impurity phases formed with increasing doping or sintering temperature were found to provide capability of tailoring magnetic properties. Thermal changes occurring in the as-prepared sample with increasing temperature till the final phase formation were clarified using thermal-gravimetric (TG) and differential thermal analysis (DTA). Formation of the fully crystallized orthorhombic phase for BaFe2O4 was reported to extend from 691 to 914 °C. X-ray diffraction (XRD) patterns of all samples were used to confirm and analyze phase formation, phase purity, lattice parameters, strain, and crystallite size. The latter was determined by three well-known Abstract iv methods; namely, Scherrer formula, and two Williamson-Hall methods. Lattice parameters and unit cell volume were estimated with quite reasonable accuracy. Non-monotonic behaviour of the unit cell volume was observed with increasing x. High resolution transmission electron microscope (HRTEM) images of the nanoparticles confirmed both the orthorhombic shape and the particle size obtained from XRD calculations. Furthermore, Fourier-transform infrared (FTIR) spectra were used to confirm the recorded phase(s) and to detect the higher valence states of Fe and Co cations. Magnetic characteristics including saturation magnetization, remnant field, and coercivity were obtained from M-H hysteresis loops traced using vibrating sample magnetometry (VSM). Samples composition and structural properties were correlated with the VSM results suggesting the plausible tailoring of magnetic properties in promising applications. Finally, the correlation of electrical properties, including ac conductivity, dielectric constant and dielectric loss with Co2+ content, was investigated for x = 0.0 and 0.2 for both systems, using LCR meter.