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Showing papers by "V. R. K. Murthy published in 2010"


Journal ArticleDOI
TL;DR: In this article, polycrystalline NiCuZn soft ferrites with stoichiometric iron were prepared by a novel microwave sintering method, and the powders were calcined, compacted and sintered at 950°C for 30min in a microwave Sintering furnace.

69 citations


Journal ArticleDOI
TL;DR: In this paper, polycrystalline MgCuZn ferrites with chemical formula Mg 0.50-x Cu x Zn 0.30 were prepared by microwave sintering method.

64 citations


Journal ArticleDOI
TL;DR: In this paper, low temperature microwave sintered NiCuZn and MgCZn ferrites with compositions Ni0.35Cu0.05Zn0.60Fe2O4 and mg0.6c2o4 were synthesized by conventional mixed oxide method, and the scanning electron micrographs of both the ferrite samples appear to be very similar.

63 citations


Journal ArticleDOI
TL;DR: In this article, a new ferromagnetic-dielectric particulate composites of Ni 0.5Zn 0.52Ti 0.48O 3 (PZT) and PbZr 0.95O 4−δ δ (NZF) were prepared by conventional ceramic method, and detailed studies on the dielectric properties were done confirming that the magnetoelectric interaction between the constituent phases may result in various anomalies in the composites.
Abstract: Novel ferromagnetic-dielectric particulate composites of Ni 0.5Zn 0.5Fe 1.95O 4−δ (NZF) and PbZr 0.52Ti 0.48O 3 (PZT) were prepared by conventional ceramic method. The presence of two phases in composites was confirmed by XRD technique. The variations of dielectric constant ( 𝜀 ) with frequency in the range of 100 kHz–1 MHz at room temperature and also with temperature at three different frequencies (50 kHz, 100 kHz, and 500 kHz) were studied. Detailed studies on the dielectric properties were done confirming that the magnetoelectric interaction between the constituent phases may result in various anomalies in the dielectric behaviour of the composites. It is proposed that interfaces play an important role in the dielectric properties, causing space charge effects and Maxwell-Wagner relaxation, particularly at low frequencies and high temperatures. The piezoelectric d33 constant was studied at room temperature, and the d33 constant value decreased with ferrite content. Magnetic properties like B-H loops traces were studied to understand the saturation magnetic ( Ms) and magnetic moment ( 𝜇 𝐵 ) of the present particulate composites. The magnetoelectric (ME) output was measured by varying dc bias magnetic field. A large ME output signal of 2780 mV/cm Oe was observed in the composite having 50% ferrite. The temperature variation of longitudinal modulus ( L) and internal friction ( Q−1) of these particulate composites at 104 kHz was studied in the temperature range 30°C–420°C by the composite oscillator technique. Longitudinal modulus showed a sharp minimum, and internal friction exhibits a sharp peak at ferroelectric-paraelectric phase transition. These ferroelectric-dielectric particulate composites were prepared with a view to using them as ME sensors and transducers.

22 citations


Journal ArticleDOI
TL;DR: In this article, the temperature variation of longitudinal modulus and internal friction of Pb(Zr0.52Ti0.48)O3 at 104 kHz frequency were studied in the wide temperature range of 30°C-420°C.
Abstract: Nanocrystalline powders of the composition Pb(Zr0.52Ti0.48)O3 were obtained by Mechanical alloying (high-energy ball milling). X-ray diffraction studies show that these compounds are completely into the perovskite phase. Detailed studies of electrical and mechanical properties of PZT as a function of temperature (and frequency) showed the high permittivity of 20653 at Curie transition temperature. Temperature variation of longitudinal modulus and internal friction of these ceramics at 104 kHz frequency were studied in the wide temperature range of 30°C-420°C. The internal friction measurements showed sharp stress induced relaxation peaks in the present composition corresponding to those temperatures where the minima were noticed in temperature variation of longitudinal modulus behavior. This dielectric and internal friction behaviour was explained in the light of polaron hopping mechanism and structural phase transitions in the present piezoelectric compositions.

17 citations


Journal ArticleDOI
TL;DR: In this article, a dielectric relaxation study for the hydrogen bonded binary system of polar liquid isopropyl alcohol in nonassociated liquids is carried out, using the HP-LF impedance analyzer in static region, Plunger method in microwave frequency region and Abbe's refractometer in optic region, at different temperature and mole fractions.

12 citations


Journal Article
TL;DR: In this article, the dielectric relaxation studies of propan-1-ol with alkyl benzoates (methyl benzoate and ethylbenzoate) have been carried out, for various mole fractions at different temperatures, using LF impedance analyzer, Plunger method and Abbe's refractometer in radio, microwave and optic frequency regions, respectively.
Abstract: The dielectric relaxation studies of propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) have been carried out, for various mole fractions at different temperatures, using LF impedance analyzer, Plunger method and Abbe's refractometer in radio, microwave and optic frequency regions, respectively. Kirkwood effective correlation factor, corrective Kirkwood correlation factor, Bruggeman parameter, relaxation time and thermo dynamical parameters are calculated using the experimental data. Conformational analysis of the formation of hydrogen bond in the equimolar binary mixture systems of propan-1-ol with alkyl benzoates is supported by experimental and theoretical FT-IR values.

9 citations


Journal ArticleDOI
TL;DR: In this article, microwave sintering (MS) and conventional sinterings (CS) techniques were used to obtain low-temperature-sintered MgCuZn ferrites, which possess good electromagnetic properties, as well as good microstructure.
Abstract: Mg0.40Cu0.10Zn0.50Fe1.95O4-? ferrite samples were prepared by the microwave sintering (MS) and conventional sintering (CS) techniques. The samples were then characterized by the x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) techniques. All the compositions showed single-phase cubic spinel structure. The lattice constants of MS samples were found to have lower magnitude than those of CS samples. The densities of microwave-sintered samples were higher than those of conventionally sintered samples. The temperature dependence of initial permeability was studied in the temperature range 30?150??C at 10? temperature intervals. It was noted that the initial permeability of MgCuZn ferrites prepared by the MS method was higher than that of MgCuZn ferrites prepared by the CS method. The initial permeability (?i) magnitude of about 2300 at 10?kHz is achieved for microwave-sintered (Mg0.40Cu0.10Zn0.50Fe1.95O4??) ferrite, at only 950??C sintering temperature. In addition, the sintering time of ferrites was reduced from 5?h to 20?min by using the MS technique. The low-temperature-sintered MgCuZn ferrites prepared possess good electromagnetic properties, as well as good microstructure, thus making them suitable materials for multilayer chip inductors (MLCIs) having high performance and low cost.

9 citations