DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

Nonstoichiometric series of Mg0.5-xCuxZn0.5Fe1.9O4-δ where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD). The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 °C and 400 °C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient α decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes. © 2017 Wroclaw University of Science and Technology

Nanocrystalline Pb(Zr 0.52

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

Ferromagnetic-Dielectric Ni 0.5Z

Novel ferromagnetic-dielectric particulate composites of Ni0.5Zn0.5Fe1.95O4−δ (NZF) and PbZr0.52Ti0.48O3 (PZT) were prepared by conventional ceramic method. The presence of two phases in composites was confirmed by XRD technique. The variations of dielectric constant () 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 () 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

AC Conductivity Studies of MgCuZn Ferrite

International audienceMg0.5-xCuxZn0.5Fe2O4 (x = 0 to 0.3) are synthesized by conventional ceramic double sintering technique. Temperature dependence of AC electrical conductivity is estimated in the temperature range of 30 to 200 o C and frequency dependence up to 1MHz. Room temperature conductivity is of the order of 10-8 Ω-1 m-1 and increases to 10-5 Ω-1 m-1 at higher temperatures. Temperature dependence of all the compositions follows Arrhenius law while the frequency dependence follows the double power law. The activation energies and the critical exponents evaluated supports jump relaxation model of conduction mechanism

Effect of glass on magnetic properties of microwave-processed MgCuZn nano ferrites

Lately ferrites find applications as multilayer chip inductor (MLCI) cores. During the MLCI fabrication, the core has to be sintered with an internal electrode like silver. The sintering temperature of ferrites can be reduced in many ways. In the present study, two techniques are simultaneously used for the purpose vice doping of glass and choosing to sinter using microwaves. Undoped and lead borosilicate glass-doped MgCuZn ferrites with generic formula Mg0.5Cu x Zn0.5-x Fe2O4 at x = 0.05-0.3 were synthesized by conventional solid state reaction route and were characterized for structural, surface, and magnetic properties. From X-ray diffraction studies, it was found that all the undoped and glass-doped samples were single-phase spinel structure. Glass-doped MgCuZn ferrite samples exhibited lower permeability than that of undoped MgCuZn ferrites. However, a flat frequency response was observed in the glass-doped Mg0.5CuxZn0.5-xFe2O4 samples at x = 0.1 and 0.2.The authors are thankful to Sri Krishnadevaraya University, Anantapur, for providing the experimental facilities. This work was supported by the financial assistance provided by the Defence Research and Development Organization (DRDO), New Delhi, India, by the grant No ERIP/ER/0303437/M/01/761. The corresponding author conveys her special thanks to Prof. S. Kaleemulla for final refinement of the manuscript.Scopu

DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

Nonstoichiometric series of Mg0.5-xCuxZn0.5Fe1.9O4-? where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD). The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 C and 400 C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient ? decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes.Scopu

DC conductivity and Seebeck coefficient of nonstoichiometric MgCuZn ferrites

Nonstoichiometric series of Mg0.5-xCuxZn0.5Fe1.9O4-? where x = 0.0, 0.1, 0.15, 0.2 and 0.25 has been synthesized by conventional solid state reaction route. The single phase spinel structure of the double sintered ferrites was confirmed by X-ray diffraction patterns (XRD). The ferrite series was studied in terms of DC electrical conductivity and thermoelectric power in the temperature ranging from room temperature to 300 C and 400 C, respectively. It was observed that DC electrical conductivity and Seebeck coefficient ? decreased with the increase in x. DC electrical conductivity was found to decrease by about 4 orders. All the compositions showed a negative Seebeck coefficient exhibiting n-type semiconducting nature. From the above experimental results, activation energy and mobility of all the samples were estimated. Small polaron hopping conduction mechanism was suggested for the series of ferrites. Owing to their low conductivity the nonstoichiometric MgCuZn ferrites are the best materials for transformer core and high definition television deflection yokes.Scopu

Ultra-Range Bimetallic Pt-Pd Nanospheres Deposited on Reduced Graphene Sheet as Efficient Electrocatalyst Towards Electrooxidation of Methanol

Direct methanol fuel cells (DMFCs) offers promising possibilities in meeting future energy needs in a most sustainable way. To electro oxidize methanol at anode of DMFCs, till date Pt and Pt-based materials were widely employed. To improve the utilization of precious metals it is highly desirable to disperse them on conductive carbon structures. Here, we synthesized ultra-range bimetallic platinum-palladium (Pt-Pd) nanospheres (NSs) with uniform dispersion on reduced graphene oxide (RGO) sheets by a simple hydrothermal method and studied their efficacies towards methanol oxidation reaction (MOR). From HR-TEM analysis, it was found that the synthesized bimetallic Pt-Pd NSs possess an average particles size of about 5 to 7 nm consistent with XRD data. The MOR electro catalytic activity of bimetallic PtPd-RGO NSs was higher compared to homemade mono metallic Pt-RGO, Pd-RGO catalysts and commercial E-tekPt/C

Phase transitions of the ferroelectric Na_0.5Bi_0.5TiO₃ by dielectric and internal friction measurements

This work focuses on the high temperature dielectric and mechanical spectroscopic properties of lead free relaxor Sodium Bismuth Titanate (NBT) ceramics, fabricated by conventional ceramic double sintering method. Systematic measurements of dielectric and mechanical properties have been performed as a function of temperature. A sequence of phase transitions has been studied by both dielectric and anelastic measurements. Three internal friction peaks were observed near 350, 200 and 120° C. The 350°C-peak corresponds to a transition associated with the tetragonal (P4bm) to rhombohedral (R3c) phase, and the 200°C-peak is related to the ferroelectric to antiferroelectric phase transition. The 120°C-peak could be ascribed to the interaction between the domain walls and the diffusion of oxygen vacancies in the domains