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Sujatha C.,National Institute of Technology Warangal | Reddy K.V.,National Institute of Technology Warangal | Babu K.S.,National Institute of Technology Warangal | Reddy A.R.C.,National Institute of Technology Warangal | And 2 more authors.
Journal of Physics and Chemistry of Solids | Year: 2013

Ni0.5-2xMgxCu0.05Zn 0.45+xFe2O4 (x=0, 0.04, 0.08, 0.12, and 0.16) ferrite samples were prepared through sol-gel method using polyvinyl alcohol as a chelating agent. Structural, magnetic, dielectric and electrical properties of the sintered samples were investigated using the characterisation techniques such as X-ray Diffractometer, Vibration sample magnetometer and impedance analyser respectively. X-ray diffraction patterns confirmed the formation of single phase cubic spinel structure of the samples. FTIR spectra showed two prominent bands (400 cm-1 and 600 cm-1) corresponding to characteristic of ferrites. Substitution of Mg and Zn for Ni showed gradual decrease of both magnetisation and coercivity. Magnetic permeability showed increasing trend with composition due to low anisotropy constant of Mg and Zn compared to Ni. Dielectric properties of the samples showed that both the dielectric constant as well as the dielectric loss factor was decreased with the composition. Cole-Cole plots consist of distorted semicircle with increasing diameter as a function of composition indicating improved resistance of the samples. The effect of substitution of Mg and Zn for Ni in NiCuZn ferrite system resulted in improved permeability with high cut off frequency, reduced dielectric losses and enhanced resistance of the samples. © 2013 Elsevier Ltd. Source


Sujatha Ch.,National Institute of Technology Warangal | Venugopal Reddy K.,National Institute of Technology Warangal | Sowri Babu K.,National Institute of Technology Warangal | Ramachandra Reddy A.,National Institute of Technology Warangal | And 2 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2013

Mg substituted NiCuZn ferrites were prepared through sol-gel method using polyvinyl alcohol (PVA) as a chelating agent. The samples after annealing at 500 C to remove PVA were sintered at 950 C for 1 h. The structural and electromagnetic properties of the samples were investigated. All the samples showed single phase spinel structure with increased lattice constant as a function of Mg concentration. The morphology reveals polyhedral shaped grains with increased grain size as a function of Mg composition. Dielectric parameters showed low values at higher frequencies. The initial permeability increased with Mg substitution in place of Ni in accordance with the microstructure. The samples sintered at low temperature having low dielectric losses and improved permeability along with the high frequency stability of permeability find applications in multilayer chip inductors. © 2013 Elsevier B.V. Source


Ganga Swamy D.R.S.,Government Polytechnic | Chaitanya Varma M.,Gandhi Institute of Technology and Management | Bharadwaj S.,Gandhi Institute of Technology and Management | Sambasiva Rao K.,Andhra University | Rao K.H.,RGU IIIT Nuzvid
International Journal of Modern Physics B | Year: 2015

Ni0.65-xMgxZn0.35Fe2O4 (x = 0, 0.4, 0.8, 0.10, 0.12 and 0.16) samples have been synthesized by sol-gel method using polyvinyl alcohol (PVA) as chelating agent. The synthesized samples were sintered at 1000 °C for 1 h. The X-ray diffraction (XRD) confirms single phase spinel structure and scanning electron microscope (SEM) confirms the uniform grain with increasing grain growth with increase concentration of magnesium (Mg) (x). A slight increase in saturation magnetization (VSM) has been observed for low concentrations of magnesium which disappear for higher concentrations of magnesium (x > 0.12) in these materials. Decrease in room temperature DC resistivity with magnesium concentration has been attributed to grain growth. The permeability measured for the ferrites exhibits high permeability for increase in the magnesium content. The permeability behavior is understood on the basis of domain wall contribution and grain growth. Frequency dependence of permeability as measured suggests that the suitability of all the samples for high frequency core applications as the operating frequency lies beyond 110 MHz. © 2015 World Scientific Publishing Company. Source


Sujatha C.,National Institute of Technology Warangal | Reddy K.V.,National Institute of Technology Warangal | Babu K.S.,National Institute of Technology Warangal | Reddy A.R.,National Institute of Technology Warangal | Rao K.H.,RGU IIIT Nuzvid
Ceramics International | Year: 2012

Mg 0.5Cu 0.05Zn 0.45Fe 2O 4 nanoparticles were prepared through sol-gel method using polyvinyl alcohol as a chelating agent. The as prepared sample was annealed at three different temperatures (500 °C, 700 °C and 900 °C). The phase formation, morphology and magnetic properties with respect to annealing temperature were studied using the characterisation techniques like X-ray diffraction (XRD) as well as Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM), respectively. The crystallite size and magnetisation showed increasing trend with annealing temperature. The coercivity increased up to a particular annealing temperature and decreased thereafter, indicating transition from single domain to multi domain state with increasing annealing temperature. Further, to know the suitability of the material, as a ferrite core, in multilayer chip inductors, the powder sample annealed at 500 °C was compacted in the form of torroids and sintered at three different temperatures (800 °C, 900 °C and 950 °C). The permeability showed increasing trend with the increase of sintering temperature since the permeability depends on microstructure. The frequency dispersion of permeability, for the sintered samples, demonstrated high frequency stability as well as high operating frequency. The cut-off frequency for the sintered samples 800 °C, 900 °C and 950 °C is 32 MHz, 30.8 MHz and 30.4 MHz, respectively. © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Source


Gangaswamy D.R.S.,Government Polytechnic | Gangaswamy D.R.S.,Andhra University | Varma M.C.,Gandhi Institute of Technology and Management | Bharadwaj S.,Gandhi Institute of Technology and Management | And 2 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2015

A series of magnesium-doped Ni0.65−xMgx Zn0.35Fe2O4 (x = 0.00, 0.04, 0.08, 0.10, 0.12, 0.16) ferrites have been synthesized using sol–gel and solid-state techniques. Sol–gel-synthesized ferrites were sintered at 1000 °C/2 h whereas solid-state-prepared ferrites were sintered at 1250 °C/2 h. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies confirm the spinel phase, and cation ion distribution has been estimated for both the batches using these studies. Magnetic measurements indicate the increase of saturation magnetization (Ms) up to x < 0.10 and decreases for further increase in concentration of magnesium. The Curie temperature of the samples was found to be decreasing with increase in concentration of Mg2+ ions in both the batches. © 2015 Springer Science+Business Media New York Source

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