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Showing papers by "V. R. K. Murthy published in 2012"


Journal ArticleDOI
TL;DR: In this paper, the authors measured the microwave dielectric properties of Ca1−xCdxMoO4 ceramics using solid-state reaction method and calculated the bond valences of A-, B-site cation, and oxygen.
Abstract: Ca1−xCdxMoO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ceramics were prepared by solid-state reaction method. Tetragonal scheelite structure with I41/a space group was observed in all these compositions. Microwave dielectric properties such as quality factor (Q × f), dielectric constant (er), and temperature coefficient of resonant frequency (τf) were measured in the microwave frequency range. Rietveld refinement was performed on all these compositions and bond valences of A-, B-site cation, and oxygen were calculated. Influence of these structural parameters on the microwave dielectric properties was examined. Q × f was correlated with the average covalence of A-, B-site cations. The variation in er was explained with ionic polarizability of Cd+2 ions. The deviation of observed polarizability from theoretical polarizability and τf of all these compositions were explained with oxygen bond valence. The well-sintered Ca1−xCdxMoO4 ceramics showed highly promising microwave dielectric properties (er = 8–10, Q × f = 46000–53000 GHz and τf = −22 to −57 ppm/°C).

40 citations


Journal ArticleDOI
TL;DR: In this article, a single phase Zn0.7Mg0.3TiO3 samples were sintered at 1100°C for different durations from 2 to 20h.
Abstract: Using solid-state reaction route and high-energy ball milling technique Zn1−xMgxTiO3 (x = 0–0.5) compositions were synthesized. These ball milled samples were sintered at 1100°C for 2 h and microwave dielectric properties such as dielectric constant (e’), quality factor (Q), and temperature coefficient of resonant frequency (τf) were studied. Significant improvement in quality factor of ~ 65% was observed for x = 0.3. To understand the effect of sintering duration on the microwave dielectric properties, single phase Zn0.7Mg0.3TiO3 samples were sintered at 1100°C for different durations from 2 to 20 h. The grain size increases with sintering duration and it influences to enhance the microwave dielectric properties and as a result, the quality factor further improved by three times. The dielectric constant and temperature coefficient of resonant frequency showed a slight improvement of ~ 10%–15% with sintering duration.

38 citations


Journal ArticleDOI
TL;DR: In this article, the effect of zinc ion substitution for nickel on structural and magnetic properties of NiZn ferrites is reported and the initial permeability increases greatly with increasing Zn content and sintering temperature.
Abstract: The effect of zinc ion substitution for nickel on structural and magnetic properties of NiZn ferrites is reported. The spinel ferrite system Ni1-xZnxFe2O4 with x = 0.2, 0.3, 0.4 and 0.5 was prepared by microwave sintering method. The uniaxially pressed samples were sintered at various temperatures such as 900°C, 1000°C and 1100°C for 30 min. X-ray diffraction patterns of the samples indicate the formation of single-phase cubic spinel structure. SEM micrographs show that grain size increases with increasing zinc content and sintering temperature. The elemental composition of these ferrites was analyzed by EDS. Lattice constant increases with increase in zinc content, obeying Vegard’s law. The effect of composition and sintering temperature on initial permeability as the function of frequency and temperature was studied. The initial permeability of NiZn ferrite increases greatly with increasing Zn content and sintering temperature. The dependence of initial permeability with respect to temperature shows the decrease in the Curie point with increase in zinc content, is the normal behavior of ferrites. The relative loss factor $$ ({{{\tan \delta }} \left/ {{{\mu_i}}} \right.}) $$ of the order of 10−2 to 10−5 in the frequency range from 100 Hz to 1 MHz indicates that the prepared ferrites have relatively high purity.

37 citations


Journal ArticleDOI
TL;DR: In this paper, the dielectric permittivity of propan-1-ol with alkyl benzoates with various mole fractions at different temperatures was studied by determining the dielectionric permitivity using - LF impedance analyzer, microwave bench and Abbe's refractometer in radio, microwave and optic frequency regions respectively.
Abstract: The molecular interactions between the polar systems propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures were studied by determining the dielectric permittivity using - LF impedance analyzer, microwave bench and Abbe's refractometer in radio, microwave and optic frequency regions respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of propan-1-ol with alkyl benzoates for the measurement of dipole moment using PC Spartan and Argus lab Modeling softwares and these theoretical values are in good agreement with the experimental values. These studies can give information on its structure and interaction.

7 citations


Journal ArticleDOI
TL;DR: The magnetite (Fe3O4) nanoparticles (0.5 wt%) of size less than 20 nm doped in p-n-alkyl benzoic acids where n varies from heptyl (7) to nonyl (9) are prepared and the presence of Fe
Abstract: The magnetite (Fe3O4) nanoparticles (0.5 wt%) of size less than 20 nm doped in p-n-alkyl benzoic acids where n varies from heptyl (7) to nonyl (9) are prepared and the presence of Fe

3 citations