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

Scanning Electron Microscopic Studies of Microwave Sintered Al-SiC Nanocomposites and Their Properties

Al-metal matrix composites (AMMCs) reinforced with diverse volume fraction of SiC nanoparticles were synthesized using microwave sintering process. The effects of the reinforcing SiC particles on physical, microstructure, mechanical, and electrical properties were studied. The phase, microstructural, and surface analyses of the composites were systematically conducted using X-ray diffraction (XRD), scanning electron microscope (SEM), and surface profilometer techniques, respectively. The microstructural examination revealed the homogeneous distribution of SiC particles in the Al matrix. Microhardness and compressive strength of nanocomposites were found to be increasing with the increasing volume fraction of SiC particles. Electrical conductivity of the nanocomposites decreases with increasing the SiC content. ? 2018 M. A. Himyan et al.This publication was made possible by NPRP Grant 7159-2-076 from Qatar National Research Fund (a member of the Qatar Foundation).Scopu

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

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

Synthesis and Characterization of Ultrafine and Porous Structure of Magnesium Ferrite Nanospheres

Porous sphere-shaped magnesium (MgFe2O4) spinel ferrite particles were synthesized with high yields, crystallinity and purity through an easy, quick, reproducible and low-temperature hydrothermal synthesis route starting from an aqueous suspension of coprecipitated metal oxalates. The structural and morphological properties of the prepared materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy and N2 adsorption–desorption measurement. Results show that the obtained MgFe2O4 particles are nearly spherical in shape and about 100-250 nm in mean diameter. Every magnetic microsphere is made of many ultrafine MgFe2O4 nanoparticles and porous in structure. The obtained sphere-shaped products exhibited a saturation magnetization of 70.25 emu/g and a coercivity of 326.41 Oe at room temperature

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

Microwave sintering, characterization and magnetic properties of double perovskite La2CoMnO6 nanoparticles

Double perovskite La2CoMnO6 (LCMO) nanoparticles were successfully synthesized by a convenient, environmentally friendly, inexpensive and efficient chemical co-precipitation process and subsequently sintered at 900 degrees C/10 min using microwave sintering (MW) for the first time. The crystal structure, morphology, elemental and magnetic properties were characterized in detail. The TEM image of the MW prepared powder reveals that the particle size is in the range of 50-70 nm. The presence of functional groups and chemical bonding is confirmed by FM. The super-paramagnetism is observed with the magnetic saturation (M-s) of 73.3 emu/g. Moreover, BET surface areas were measured at the liquid nitrogen temperature by nitrogen adsorption. (C) 2014 Elsevier B.V. All rights reserved

Effect of sintering temperature on the structural and magnetic properties of MgFe2O4 ceramics prepared by spark plasma sintering

Spark plasma sintering (SPS) is a powerful technique to produce fine grain dense ferrite at low temperature. This work was undertaken to study the effect of sintering temperature on the densification, microstructures and magnetic properties of magnesium ferrite (MgFe2O4). MgFe2O4 nanoparticles were synthesized via sol–gel self-combustion method. The powders were pressed into pellets which were sintered by spark plasma sintering at 700–900 °C for 5 min under 40 MPa. A densification of 95% of the theoretical density of Mg ferrite was achieved in the spark plasma sintered (SPSed) ceramics. The density, grain size and saturation magnetization of SPSed ceramics were found to increase with an increase in sintering temperature. Infrared (IR) spectra exhibit two important vibration bands of tetrahedral and octahedral metal-oxygen sites. The investigations of microstructures and magnetic properties reveal that the unique sintering mechanism in the SPS process is responsible for the enhancement of magnetic properties of SPSed compacts