Raju Kumar; Rashmi Rani; Seema Sharma
Abstract
Polycrystalline samples of 1- x(Na0.5 K0.5)(Nb0.95 Ta0.05) ) -x(Bi Fe)O3 with x=0, 0.003, 0.005, 0.007) hereby denoted as NKNT-BF were prepared by the mixed oxide method. Preliminary structural studies carried out by X-ray diffraction technique showed the formation of perovskite structure with orthorhombic ...
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Polycrystalline samples of 1- x(Na0.5 K0.5)(Nb0.95 Ta0.05) ) -x(Bi Fe)O3 with x=0, 0.003, 0.005, 0.007) hereby denoted as NKNT-BF were prepared by the mixed oxide method. Preliminary structural studies carried out by X-ray diffraction technique showed the formation of perovskite structure with orthorhombic symmetry. Addition of BF in the NKNT system lowered the sintering temperature by 500C. The nature of the frequency dependence of ac conductivity of NKNT compounds follows Jonscher power law. Complex impedance and modulus spectra confirm the significant contribution of both grain and grain boundary to the electrical response of the materials. Above the ferroelectric–paraelectric phase transition temperature, the electrical conduction is governed by the thermal excitation of charge carriers from oxygen vacancies exhibiting Negative temperature coefficient (NTCR) behaviour. Detailed study on the multiferroic properties (where magnetism and ferroelectricity are strongly coupled together) of the system is under process which is likely to form key components in the development of future technology, for example, in memories and logic devices.
Seema Sharma; Rashmi Rani; Radheshyam Rai; T. S. Natarajan
Abstract
One dimensional nanofibers of organic and inorganic materials have been used in filters, optoelectronic devices, sensors etc. It is difficult to obtain ultra fine fibers of inorganic materials having lengths in the order of millimeter as they tend to break during formation due to thermal and other mechanical ...
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One dimensional nanofibers of organic and inorganic materials have been used in filters, optoelectronic devices, sensors etc. It is difficult to obtain ultra fine fibers of inorganic materials having lengths in the order of millimeter as they tend to break during formation due to thermal and other mechanical stresses. In this study, we have investigated the mechanism to prevent the defect formation and the breaking of CuO nanofibers by using optimized heat flow rates. CuO nanofibers were obtained by heat treating the poly(vinyl acetate) PVA composite fibers formed by electrospinning. The morphology and structural characteristics of prepared samples were investigated by Scanning electron microscopy, Transmission electron microscopy and X-ray diffraction. It was found that the morphology of the composite and annealed nanofibers could be influenced by the concentration of the polymer content. A lower concentration favors the formation of defects along the fiber and the number of defects reduces when the concentration is increased.
