Mamata Maisnam

EFFECT OF MICROWAVE SINTERING ON THE STRUCTURAL AND ELECTRICAL PROPERTIES OF Li0.51Zn0.2Ti0.2V0.01Fe2.08O4 FERRITE

Effect of microwave sintering on the structural and electrical properties of

Dielectric Properties of Vanadium Substituted Lithium Zinc Titanium Ferrites

{\rm Li}^{+}_{0.51}{\rm Zn}^{2+}_{0.2}{\rm Ti}^{4+}_{0.2}{\rm V}^{5+}_{0.01}{\rm Fe}^{3+}_{2.08}{\rm O}^{2-}_{4}

ELECTRICAL CONDUCTION IN SUBSTITUTED Li-FERRITES PREPARED BY MICROWAVE PROCESSING

is studied in comparison with that of conventionally sintered one. The technique is advantageous in terms of significantly reduced size of microwave kilns and rapid heating compared to the cumbersome and slow heating of conventional sintering technology. Microwave sintering produced enhanced densification and much finer microstructures. The DC resistivity is markedly increased. Microwave sintering reduces chances of evaporation of lithium and oxygen during sintering of lithium based ferrites resulting in formation of lesser ferrous ions. This has profound effect on the electrical properties of microwave sintered ferrites. The dielectric constant is significantly reduced possibly due to reduced space charge polarization and the temperature dependence of the dielectric properties are also studied.

Improved Properties of Li-Mn-Ti Ferrites by Microwave Sintering

This paper reports the influence of vanadium substitution on the properties of Li–Zn–Ti ferrite. Samples with compositional formula Li0.5+tZn0.2Ti0.2VtFe2.1-2tO4 (t ranging from 0 to 0.25 in steps of 0.05) were prepared by the conventional sintering technique. XRD analysis confirmed all the samples to be single phase with spinel structure. The lattice constant a density, Curie temperature and Saturation magnetization were measured. The dielectric behaviour was studied as a function of frequency and temperature. The dielectric behaviour showed dispersion with the frequency in the range 100 Hz to 1 MHz. The dielectric constant increases with the increase of temperature for all the samples. The possible mechanisms involved are discussed.

Higher d.c. resistivity of Li-Zn-Cd ferrites prepared by microwave sintering compared with conventional sintering

Samples with representative formula Li0.45Ni0.1Mn0.1Fe2.35O4 have been sintered by conventional sintering technique and microwave sintering technique. Both the samples showed single-phase with spinel structure. The lattice constant for the microwave sintered (MS) sample showed a lower value than the conventionally sintered (CS) sample. The density of the MS sample has been found to be higher than the CS sample. And MS sample showed a higher value of resistivity and activation energy compared to the CS sample. The possible mechanisms are discussed.

ELECTRICAL PROPERTIES OF Cd2+ SUBSTITUTED Li–Zn FERRITES

Substituted Li-ferrites are attractive materials for research due to their important properties like high Curie temperature leading to high thermal stability, high and wide range of saturation magnetization, low stress sensitivity of remanence and they are very good dielectric materials. The properties are very sensitive to the type and amount of substituents, method of preparation and sintering conditions. Attempts to minimize loss of lithia and oxygen during sintering by adopting various processing method, which otherwise is very difficult to control technologically by conventional method, has been a continuous efforts for the researchers.The present paper reports the improvements that arise in the properties of Li-Mn-Ti ferrite by using novel microwave (MW) processing technique. Mn4+ and Ti4+ substituted Li-ferrites having the compositional formula Li0.60Mn0.1Ti0.1Fe2.20O4 were prepared by both the conventional and microwave techniques. XRD confirmed the formation of single phase with spinel structures in both the samples. Dielectric properties were studied as a function of temperature. Dielectric properties of MW processed sample were found to be more stable with temperature. Significant improvement in the d. c. resistivity was observed in theMWsintered sample over the conventional sintered sample. The possiblemechanisms involved are discussed.

Microwave sintering of lithium nickel manganese ferrites and their properties

Cd2+-substituted Li-Zn ferrites having the general formula Li0.4−x/2+Zn0.22+Cdx2+Fe2.4−x/23+O42− where x = 0.02, 0.03 and 0.04 have been prepared by both microwave sintering and conventional sintering. In the former case, sintering was done at 1050 °C for 25 min, whereas in the latter case sintering was done at 1050 °C for 6 h. The various structural properties, microstructures and d.c. resistivity of the samples prepared by the two techniques were compared. The study showed higher d.c. resistivity and higher activation energies in the samples prepared by microwave sintering. The mechanisms pertaining to the results are discussed.

Effect of microwave sintering on the properties of Li-Zn-Ti-V ferrite

Cd2+ substituted Li–Zn ferrite with compositional formula Li0.4-x/2Zn0.2CdxFe2.4-x/2O4 with x = 0.02, 0.03 and 0.04 were prepared by the conventional double sintering ceramic technique. XRD technique confirmed the formation of single phase with spinel structure. The substitution causes an increase in the lattice constant, density and DC resistivity, while the Curie temperature and dielectric constant decreases with Cd2+ substitution. The mechanisms involved are discussed.

Influence of sintering technique on the characteristics of Li–Co nanoferrites

Studies on the significant changes in the structural, microstructural, magnetic and electrical properties of microwave sintered lithium nickel manganese ferrites over the conventionally prepared one were carried out. Microwave sintering reduces chances of evaporation of lithia or oxygen during sintering of lithium based ferrites further resulting in reduction of formation of ferrous ions. This has profound effect on the magnetic and electrical properties of the final product. Saturation magnetization value has been found to be slightly reduced with microwave sintering. Low dielectric constant values were measured in the composition prepared by microwave sintering. Increased activation energy obtained in the sample sintered using microwave field offer greater resistance to the thermal activation of the polarizable charges. The rapid rise in the dielectic constant with temperature has been significantly shifted to higher temperature.

Structural and electrical studies of sol–gel synthesized nanocrystalline hexagonal yttrium iron manganite ceramics

Effect of microwave sintering on the various properties of Li⁺<inf>0.51</inf>Zn²⁺<inf>0.2</inf>Ti⁴⁺<inf>0.2</inf>V⁵⁺<inf>0.01</inf>Fe³⁺<inf>2.08</inf>O²⁻<inf>4</inf> is evaluated in comparision with the conventionally sintered one. The technique is advantageous in terms of significantly reduced size of microwave kilns and the rapid heating compared to the conventional sintering technology. The product however yields higher densities, d. c. resistivity and saturation magnetization values for the microwave sintered sample. The Curie temperature is slightly lowered. Reduction in material loss during sintering and hence availability of fewer Fe²⁺ ions is one presumptions for such changes in the properties. The dielectric constant is significantly reduced possibly due to reduced space charge polarization. The temperature dependence of the dielectric properties is quite insignificant.