Nimish H. Vasoya; Kiran G. Saija; Akshay R. Makadiya; Tushar K. Pathak; Urmila M. Meshiya; Pooja Y. Raval; Kunal B. Modi
Abstract
The compositional dependence of the real (ε') and imaginary (ε'') parts of complex dielectric permittivity (ε*) and loss tangent (tan d) for Mn0.7+xZn0.3SixFe2-2xO4 (x = 0.0, 0.1, 0.2 and 0.3) spinel ferrite series was investigated over wide frequency (f = 20 Hz to 1 MHz) and ...
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The compositional dependence of the real (ε') and imaginary (ε'') parts of complex dielectric permittivity (ε*) and loss tangent (tan d) for Mn0.7+xZn0.3SixFe2-2xO4 (x = 0.0, 0.1, 0.2 and 0.3) spinel ferrite series was investigated over wide frequency (f = 20 Hz to 1 MHz) and temperature (T = 300 K to 673 K) ranges. Frequency dependence of ε',ε'' and tan δ has been explained based on the two-layer model of dielectrics. The nonlinear relationship between ε'(f) and σ'(f) suggests multi-relaxation process and formation of a broad hump in ε'(f, T) plots indicates collective contributions from electrons and holes to the polarization. The scaling by normalized frequency (f/fc) and scaled frequency (f/σdc) are found successful for ε' in high-frequency regime only while scaling found successful for ε'' over the whole range of frequency. The suitability of various scaling parameters was also tested for the master curve generation. The co-existence of localized and delocalized relaxations is verified.
Sajad Ahmad Mir; M. Ikram; K. Sultan; Z. Habib; H. Kausar; K. Asokan
Abstract
Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain ...
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Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain size (0.2 μm to 0.3 μm) with an increase in Ni doping. The influences of Ni doping on optical energy band gap are investigated in the wavelength range of 200-800 nm. Dielectric properties (dielectric constant and loss) for SmFe1-xNixO3 were studied in the temperature range 100-400K and in the frequency range 20 kHz-1MHz. AC conductivity of pristine sample is found to be less than Ni doped samples. Various possibilities were explored to explain the observed dielectric and electric behavior of Ni doped SmFeO3 ceramics.
Gagan Kumar; Virender Pratap Singh; Arun Kumar; Jyoti Shah; Shalendra Kumar; B.S. Chauhan; R.K. Kotnala; M. Singh
Abstract
We investigated the effects of In 3+ and Co 2+ substitutions on the structural and magnetic properties of Mg-Mn ferrites. The cation distribution technique was taken into account to estimate the magnetic interactions. Cation distribution was also used to investigate the ionic radii of tetrahedral and ...
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We investigated the effects of In 3+ and Co 2+ substitutions on the structural and magnetic properties of Mg-Mn ferrites. The cation distribution technique was taken into account to estimate the magnetic interactions. Cation distribution was also used to investigate the ionic radii of tetrahedral and octahedral sites, oxygen positional parameter, site bond as well as edge lengths, bond lengths and bond angles. The ionic radius of tetrahedral site and octahedral site was observed to increase with the incorporation of In 3+ and Co 2+ ions respectively. Theoretical lattice parameter was observed to increase with the substitution of In 3+ and Co 2+ ions. In 3+ substitution resulted in weakening of super-exchange interactions while in Co 2+ substituted Mg-Mn ferrites, anisotropy was observed to play a decisive role in addition to bond lengths and bond angles.
M. Raghasudha; D. Ravinder; P. Veerasomaiah
Abstract
Nano-ferrites of the composition Mg Crx Fe2-xO4 (where x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized at a very low temperature (180°C) by Citrate-gel auto combustion method. The as synthesized powders were sintered at 500 0 C for four hours in an air and were characterized by X-ray diffraction ...
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Nano-ferrites of the composition Mg Crx Fe2-xO4 (where x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized at a very low temperature (180°C) by Citrate-gel auto combustion method. The as synthesized powders were sintered at 500 0 C for four hours in an air and were characterized by X-ray diffraction (XRD) which confirmed the formation of cubic spinel structure of ferrites. The crystallite size was in the range of 7 to 23nm for different compositions with the significant decrease of ~16nm in response to the increase in Cr substitution. Such low nano sized ferrites are desirable for variety of applications like, in magnetic data storage and in targeted drug delivery, etc. Morphological studies by Scanning Electron Microscopy (SEM) revealed formation of largely agglomerated, well defined nano particles of the sample. Elemental composition characterizations of the prepared samples were performed by Energy Dispersive Spectroscopy (EDS) which shows the presence of Mg, Cr, Fe and O without precipitating cations. The FTIR spectral studies at room temperature in the range of 400 to 800cm-1 showed two strong absorption bands. The high frequency band (ν1) around 600 cm -1 is attributed to the intrinsic vibrations of tetrahedral complexes and the low frequency band (ν2) around 400 cm -1 is due to octahedral complexes. The spectra showed the characteristic peaks of ferrite sample. The observed results can be explained on the basis of composition and crystal size.
Surender Kumar; Tukaram J. Shinde; Pramod N. Vasambekar
Abstract
Powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the spinel structure of nanocrystalline Ferrites with composition Mn1-xZnxFe2O4 (x = 0.2, 0.4, 0.6 and 0.8) prepared by oxalate coprecipitation technique and followed by microwave heating ...
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Powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the spinel structure of nanocrystalline Ferrites with composition Mn1-xZnxFe2O4 (x = 0.2, 0.4, 0.6 and 0.8) prepared by oxalate coprecipitation technique and followed by microwave heating of precursors. Effect of composition on the lattice constant, x-ray density, crystallite size was studied. Crystallite size and x-ray density increases with increase in Zinc content. The face centered cubic spinel structure has undergone deviation from ideality. A correlation exists between splitting of infrared absorption bands and lowering of composition dependent crystalline symmetry. This preparation technique could be used for synthesis of materials which use microwave transparent precursors.
P. Raju;S. R. Murthy
Abstract
The nanocomposites of x TiO2+(1-x)CoF2O4 (≤x≤1) powders were synthesized using microwave-hydrothermal method at a low temperature of 165°C/45min. The synthesized powder was characterized by using XRD, TEM, FTIR and DSC. The particle size was obtained from TEM study varies from 18nm to 34nm ...
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The nanocomposites of x TiO2+(1-x)CoF2O4 (≤x≤1) powders were synthesized using microwave-hydrothermal method at a low temperature of 165°C/45min. The synthesized powder was characterized by using XRD, TEM, FTIR and DSC. The particle size was obtained from TEM study varies from 18nm to 34nm for all the nanopwders. DSC curve of composites shows no anatase to rutile phase transformation. As synthesized powder was densified using a microwave sintering method at 500°C/30min. In the XRD patterns of sintered composite samples, no peaks other than TiO2 and CoFe2O4 were observed. The grain sizes of the composites have been estimated from SEM pictures and they are in between 54 to 78nm. The dielectric properties were measured in the frequency range of 100 Hz to 1 MHz. The frequency variation of dielectric properties is understood with the help of Maxwell–Wagner type of interfacial polarization, which is in agreement with Koop’sphenomenological theory. The thermal variation of dielectric constant and loss studies were also undertaken at a constant frequency of 1kHz. Magnetic properties were also measured on all the composite samples at room temperature. The saturation magnetization (Ms) of the samples decreases with an increase of TiO2 content in CoFe2O4.
