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Mn[sub x]Ni[sub 0.5-x]Zn[sub 0.5]Fe[sub 2]O[sub 4] ferrites with x = 0.05, 0.1, 0.2, 0.3, and 0.4, have been synthesized by the citrate precursor method and investigated for their magnetic properties. The initial relative permeability is observed to increase with increase in manganese concentration up to x = 0.2 followed by a decrease, the maximum value being 632. An initial increase followed by a subsequent decrease of saturation magnetization with increase in x is observed. Curie temperature is observed to decrease continuously from 488 to 418 °C when x increases from 0.05 to 0.4. Frequency variation of complex initial permeability indicates that resonance peak due to domain wall oscillations is at a frequency above 13 MHz. Saturation magnetization is observed to increase by about 22% when the sintering temperature is increased from 1200 to 1400 °C. Initial permeability and B-H loops are observed to increase and constrict, respectively, with increase in sintering temperature. [ABSTRACT FROM AUTHOR]

The dielectric properties of Mn[sub x]Ni[sub 0.5-x]Zn[sub 0.5]Fe[sub 2]O[sub 4] ferrites with x varying from 0.05 to 0.4 synthesized by the citrate precursor method have been investigated as a function of frequency, temperature, composition, and sintering temperature. An increase in the dielectric constant is observed with the increase in Mn concentration except for x = 0.3. Dispersion in the dielectric constant with frequency in the range of 100 Hz-1 MHz is observed. Resonance peaks were observed in tan δ[sub ∈] versus frequency curves for all samples. A shift in the resonance frequency towards higher frequency is observed with increase in temperature. The peak height also increases with increase in temperature. Possible mechanisms contributing to these processes have been discussed. From the temperature variation of the dielectric relaxation, activation energies for various samples have been calculated and compared with those obtained from dc resistivity. [ABSTRACT FROM AUTHOR]

In this paper, we are reporting structural, dielectric, ferroelectric and magnetic properties of polycrystalline composites (ferrite and ferroelectric) of PZT (PbZr0.55Ti0.45O3) + CNFO (Co0.8Ni0.2Fe2O4). The sample with composition x CNFO + (1-x) PZT (x = 0.00, 0.05, 0.10, 0.15 and 1.00) were prepared using the solid state double sintering method. Here the ratio x: (1-x) of two components is by weight. X-ray diffraction (XRD) studies show that lattice constant and tetragonality decreases with increasing ferrite content. Dielectric constant was found to decrease with increase in amount of CNFO. The value of tangent loss (tanδ) was reasonably low (< 0.04) for all the samples. Ferroelectric and ferrimagnetic behavior was confirmed by observing P-E and M-H hysteresis loop, respectively. The room temperature magnetoelectric coupling coefficient (α = dE/dH) was measured as a function of applied DC magnetic field. The value of α was observed to be maximum (855 μV/(cm.Oe)) at DC magnetic field of 1.7 kOe for sample with 5% CNFO. Value of piezoelectric coefficient ‘d33’ decreases from 133 to 60 pC/N. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, effect of addition of Ni0.8Co0.2Fe2O4 (NCF), prepared by three different methods namely solid state reaction method, sol–gel and co-precipitation, has been studied on microstructural, magnetic, dielectric, ferroelectric and magnetoelectric properties of multiferroic composite system 0.95 Ba0.95Sr0.05TiO3–0.05 Ni0.8Co0.2Fe2O4. Ba0.95Sr0.05TiO3 (BST) has been prepared by solid state reaction method. Titular representation of NCF samples prepared by sol–gel, co-precipitation, solid state reaction method is N–SG, N–CP, N–SS respectively and that of corresponding magnetoelectric composite is C–SG, C–CP, C–SS. X–ray diffraction analysis of the composite samples (C–SG, C–SS, C–CP) indicated the presence of both NCF and BST phases. Rietveld analysis of XRD pattern further confirmed the proper phase formation in the composite samples. Sol–gel and co-precipitation processes result in finer NCF particles as confirmed by Transmission electron microscopy (TEM). Sample N–SG possesses uniform particle size and shape. Magnetization versus magnetic field (M–H) loops of samples C–SS and C–CP possess respectively highest value of remanant magnetization and magnetic coercive field. Dielectric properties of BST, NCF and composite samples have been measured in the frequency range of 20Hz–1MHz and temperature range of 50–170°C. The composite sample C–CP results in highest value of dielectric constant in comparison to samples C–SS and C–SG. Polarization versus electric field (P – E) measurements pointed that composite sample C–SG possesses highest value of remanant and saturation polarization and C–SS possesses lowest value of coercive electric field. The composite sample C–SS possesses highest value of magnetoelectric coefficient. [Copyright &y& Elsevier]

Ferroelectric-ferrite composites are very important materials as they show both electric and magnetic properties and are drawing attention of researchers over the last few years due to their immense contribution to the improvement of science and technology. Electrical and ferroelectric properties of such ceramic materials are strongly dependent on composition and ratio of two constituents. In the present paper we are reporting the dielectric and ferroelectric properties of (1-x)Ba0.90Sr0.10TiO3- xNi0.80Zn0.20Fe2O4, (0 ≤ x ≤ 0.02 steps of 0.01) (BST-NZF) mixed phase materials. Both the constituent materials were prepared separately by conventional solid state method and then finally mixed by weight to form the mixture. The dielectric properties were measured as a function of temperature at 100 Hz, 1 kHz, 10 kHz and 100 kHz frequencies. P-E hysteresis loops were recorded at 20 Hz for all the mixture samples. Remanent polarization was found to decrease with increase in ferrite content. Magnetization measurements show the samples to be in ferromagnetic state. Structural analysis was done by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The article reports on the improvements that arise in the electrical and structural properties of Li-Mn-Ti ferrite with the formula Li0.60Mn0.1Ti0.1Fe2.20O4 using novel microwave (MW) processing. It says that the formation of single phase spinel structure in both samples was confirmed by X-ray diffraction. It adds that the studies of dielectric properties as temperature function show the stability of dielectric properties with temperature.

Being materials with a large number of interesting properties, ferroelectric-ferrite based composites have recently been developed. People are showing a great interest in these materials due to some unique properties like magnetoelectric effect in addition to the ferroelectric, dielectric and magnetic properties. After a review of literature it is found that the variation in different properties of PZT ceramics is found to depend on the amount of ferrite content. In this paper, we are reporting the variation in ferroelectric properties of PbZr0.65Ti0.35O3 (PZT) by varying Ni-Zn ferrite (NZF) content. The studied system having compositional formula (1-x) PZT-x NZF (0 ≤ x ≤ 0.025, in steps of 0.005), was prepared by solid state route using microwave sintering. Remanant polarization was found to be monotonically decreasing with increasing ferrite content as observed from the recorded P-E hysteresis loops for all the samples at 20 Hz. Microwave sintering results in significant improvements in properties as compared to conventionally sintered samples. [ABSTRACT FROM AUTHOR]

Ni substituted Li–Zn ferrites with compositional formulas Li0.4-0.5xZn0.2NixFe2.4-0.5xO4, where x = 0.02 ≤ x ≤ 0.1 in steps of 0.02, is synthesized by a chemical method using citrate precursors. The prepared ferrites are investigated for their structural, electrical and magnetic properties. Ni substitution significantly changes the characteristic properties of Li–Zn ferrites. There is an increase in grain growth as determined from SEM measurements. An increase in the room temperature DC resistivity is observed with the addition of Ni. The room temperature initial permeability shows an overall decrease with Ni concentration, which is explained with respect to saturation magnetization and supplemented by nuclear hyperfine field obtained from Mössbauer analysis. The variation of the complex permeability with frequency is measured over the frequency range of 100 Hz–1 MHz and dispersion is found. A possible mechanism contributing to the above process is discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A series of cobalt substituted lithium zinc ferrites having the compositional formula Li0.4-0.5xZn0.2CoxFe2.4-0.5xO4, where 0.00 ≤ x ≤ 0.1 in steps of 0.02, was prepared by the citrate precursor method. Structural studies on the prepared samples were carried out by using XRD and SEM measurements. Spinel phase structure of the samples was confirmed by XRD. From the XRD data the lattice parameter and the theoretical density were calculated. The experimental density was also determined using the Archimedes principle. Lattice parameter was observed to increase with increasing Co2+ ion concentration. The densification in both the cases, theoretical and experimental, shows an increase with composition. SEM studies carried out show that average grain diameter are in the range of 300 nm-650 nm and a fall is observed with increasing Co2+ ion content. The investigation on initial permeability as a function of composition and frequency were also undertaken. It is seen that there is decrease in the value of initial permeability with addition of Co content. The initial permeability and permeability loss show dispersion with frequency. Possible mechanisms contributing to the above processes are discussed. [ABSTRACT FROM AUTHOR]

A simple aqueous solution-based chemical methodology has been developed for the preparation of single-phase Ni1-xZnxFe2O4 nanopowder, where x = 0.2, 0.35.0.5 and 0.6. The average particle size of the synthesized powders was in the range of 30-50 nm. Precursor powders were synthesized by reacting aqueous solutions of metal nitrates with polyvinyl alcohol and sucrose and then evaporating the resulting solution to dryness. The precursors were calcined in air for 2.30 h at different temperatures ranging from 650 to 950°C. The synthesized powders were characterized by using thermogravimetric analysis-differential scanning calorimetric analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy. Change of DC electrical resistivity with change in sintering temperature and microstructure was measured by using the two-probe method. The as synthesized nanopowders possess a high room temperature resistivity of ∼106-107 Ωcm. They exhibit a good amount of magnetization in the range of 49-61 emu/g and a wide range of coercivity of 20-73 Oe. The novelty of this method lies in its simplicity and cost effectiveness. This method has the capability of being an alternative route to the other reported synthetic methods. [ABSTRACT FROM AUTHOR]

Li0.45Ni0.1Mn0.1Fe2.35O4 ferrite samples were prepared by microwave-sintering (MS) and conventional (CS) techniques. XRD studies have confirmed the single-phase spinel structure of the sample. The lattice constant was found to be 8.334 Å which is lower than that of the conventionally sintered (CS) sample. Upon microwave sintering, improved physical and electrical properties (like density, resistivity etc.) were obtained. A comparative study has been made on the dielectric behavior of samples processed by both techniques. The possible mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties, such as initial permeability and hysteresis loop properties of the chromium substituted Li–Sb ferrite system have been investigated. The SEM micrographs reveal the microstructure of the samples. The initial permeability is observed to decrease with the increase of chromium concentration. Frequency variation of permeability indicates that for all samples the resonance peak due to domain wall oscillations is at a frequency above 15MHz. The hysteresis loop parameters have been calculated from the hysteresis loop studies. The magnetic parameters are observed to decrease with higher level of substitution. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tan δ) of Li0.5+xFe2.5-2xSbxO4 ferrites, 0.10≤ x ≤0.30 in steps of 0.05 have been investigated as a function of composition, frequency and temperature. The dielectric constant showed dispersion with frequency in the range of 100 Hz–1 MHz. Peaks were observed in the tan δ versus frequency curves for almost all the samples. The temperature variation of dielectric constant for the different samples was studied at 10 kHz in the temperature range from room temperature to 433 K. Peaks were observed for some of the samples. The peaks were seen to shift towards higher temperature region as the substitution level increases. The mechanisms involved in the processes are discussed in this paper. [ABSTRACT FROM AUTHOR]

Mössbauer investigations have been carried out for the system Li[sub 0.6-0.5x]Co[sub x]Sb[sub 0.1]-Fe[sub 2.3-0.5x]O[sub 4] with 0.0≤x≤1.0, x in steps of 0.2. The observed variation of the various Mössbauer parameters like isomershift, quadrupole splitting, nuclear magnetic field and linewidth are explained in terms of cation distribution and superexchange interaction. [ABSTRACT FROM AUTHOR]

The effect of Cr[sup 3+] concentration on the various hyperfine interactions for the ferrite system Li[sub 0.5+t]Cr[sub x]Sb[sub t]Fe[sub 2.5-2t-x]O[sub 4], 0.0 ≤ x ≤ 1.0, x in steps of 0.2 and t = 0.1, have been studied at room temperature using Mössbauer spectroscopy. The isomershift and the quadrupole splitting are almost negligibly influenced by the change in chromium level. The internal nuclear magnetic fields as determined from the Mössbauer spectra and the linewidth are also studied with the variation of composition. The results have been explained on the basis of various models and a cation distribution has been worked out. [ABSTRACT FROM AUTHOR]

In this paper we report influence of titanium substitution on the structural properties and d.c. conduction behavior of Li-Zn ferrites. The samples having the compositional formula Li[sub 0.45+0.5t]Zn[sub 0.1]Ti[sub t]Fe[sub 2.45-1.5t]O[sub 4] with t varying from 0 to 1.2 in steps of 0.2 were prepared by the conventional dry ceramic method. XRD analysis showed all the samples to be single phase spinel and the lattice parameter was found to increase with increasing t. D.C. resistivity increases with Ti concentration. The possible mechanisms involved are discussed. [ABSTRACT FROM AUTHOR]

Ferrites with compositional formula Li0.49Zn0.02Mn0.06Fe2.43O4 were prepared by solid state reaction route and were sintered using conventional and microwave furnaces. The structural and electrical properties were studied and compared. Dielectric constant and tanδ were measured as a function of temperature and frequency. DC resistivity of the samples was calculated by impedance analysis in the temperature range from 25°C to 150°C. High DC resistivity (10k–100kΩm) was observed for microwave sintered ferrite sample as compared to conventionally sintered sample (2–80Ωm) in the measured temperature range. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline lithium zinc ferrites substituted with cobalt were synthesized by the citrate precursor method. X-ray diffraction was used to confirm the spinel phase. Mössbauer studies at room temperature were carried out to study the effect of cobalt concentration on the various hyperfine interactions. Variation of the saturation magnetization with respect to composition was discussed. The result shows some anomalous behaviour when cobalt is substituted to lithium ferrite in presence of zinc. [Copyright &y& Elsevier]

Single phase polycrystalline lithium ferrites modified with Zn and Mn were synthesized by solid state reaction method. The prepared samples exhibit a markedly increased value in real part of dielectric constant ( ε ) and a lowest loss tangent (tan δ ) for x =0.04 measured in the frequency range 70 Hz to 1 MHz. The saturation magnetic moment ( M s ) varies non-monotonically for different values of x . A maximum value of M s =76 emu/g has been found for x =0.02. Such results in lithium ferrite based ferrites being found rarely. [ABSTRACT FROM AUTHOR]

Abstract: Magnetoelectric composites of nickel zinc ferrite (NZF) and La substituted lead zirconate titanate (PLZT) having representative formula 0.1Ni0.8Zn0.2Fe2O4−0.9Pb1−3x/2La x Zr0.65Ti0.35O3 (x=0, 0.01, 0.02 and 0.03) were synthesized by a conventional solid state route. X-ray diffraction analysis was carried out to confirm the coexistence of individual phases. Scanning electron microscope micrographs were taken for microstructural study of the samples. Dielectric properties were studied as a function of temperature and frequency. To study ferroelectric and magnetic ordering in composite samples, P–E and M–H hysteresis loops were recorded respectively. M–H hysteresis loops were taken for electrically poled and unpoled samples to confirm magnetoelectric coupling between the two phases (NZF and PLZT). La substitution results in significant improvement in dielectric, ferroelectric and piezoelectric properties of composite samples. [Copyright &y& Elsevier]

Abstract: The dielectric properties of Li0.4−0.5x Zn0.2Co x Fe2.4−0.5x O4 ferrites with varying from 0.0 to 0.1 in steps of 0.02 synthesized by the citrate precursor method have been investigated as a function of composition and temperature. Room temperature dielectric constant studied at 1 kHz showed a decrease with addition of Co2+ ions. The variation of dielectric constant with temperature was studied at different frequencies, and an increase was observed as the temperature rises. For certain composition, at particular frequency resonance maxima could be observed in the dielectric constant versus temperature curve. The possible mechanisms responsible for the above behaviour are explained. [Copyright &y& Elsevier]

Abstract: Fine powders of Ni0.6− x Cu x Zn0.4Fe2O4, where 0≤ x ≤0.4 was prepared by the citrate precursor method. The powders were calcined at 600°C for a duration of 1h and sintered at 900°C for 3h. The effect of compositional variation on structural, dielectric and magnetic properties of the Cu substituted NiZn ferrite was investigated. X-ray diffraction measurements confirmed the formation of single-phase cubic spinel structure at such low temperature of calcinations and sintering. A maximum density of 4.7g/cm3 was obtained for the Cu substituted ferrite. The grain sizes were estimated from the SEM micrographs. The addition of copper promoted grain growth, resulting in increase in grain size. Curie temperature, however, was understandably lowered with the increase in Cu content. A saturation magnetization value of 92emu/g was obtained for the composition x =0.2. This value is higher than that reported for ferrites prepared by the conventional ceramic method. Ferrite with Cu concentration of x =0.4, showed the highest value of initial permeability. [Copyright &y& Elsevier]

Abstract: This paper reports the influence of Co2+ substitution on the structural parameters and DC resistivity of Li–Mn–Ni ferrites. Samples having the compositional formula Li0.45− x /2Ni0.1Mn0.1Co x Fe2.35− x /2O4, with ranging from 0 to 0.01 in steps of 0.002, were prepared by the conventional ceramic technique. X-ray diffraction has confirmed the single-phase spinel structure of the samples. The lattice parameter and theoretical density of the samples were determined and the latter compared with the experimental density measured by Archimedes Principle. Porosity was found to decrease with substitution. The temperature dependence of DC resistivity shows the semiconducting nature. The resistivity and activation energies increase with the increase of substitution level. [Copyright &y& Elsevier]

Abstract: Li–Zn–Ti ferrite samples, with compositional formula Li0.5+tZn0.2Ti0.2VtFe2.1-2tO4, ‘t’ ranging from 0.0 to 0.25 in steps of 0.05 were prepared by the ceramic route. XRD results confirmed the single-phase spinel structure of the samples. SEM photomicrographs have revealed the grain size of the samples. B–H loops have been traced for all the samples and the various hysteresis parameters like coercivity, remanence and remanence ratio have been studied as a function of composition. Compositional dependence of initial permeability (μi), the frequency dispersion of initial permeability and the corresponding loss, tanδμ have been studied. The possible mechanisms involved are discussed. [Copyright &y& Elsevier]

MnxNi0.5−xZn0.5Fe2O4, (x=0.05, 0.1, 0.2, 0.3, 0.4) ferrites synthesized by the citrate precursor method are investigated in the present work. Compositional variation of AC resistivity is studied and values up to 103 times greater than those for samples prepared by the conventional ceramic method are observed. It is found that resistivity decreases with increase in Mn concentration except for x=0.3, where it shows a rise. Frequency variations of both dielectric constant and relative loss factor (rlf) are reported in the present work. It is observed that dispersion in dielectric constant is greatly influenced by the Mn concentration. Possible mechanisms contributing to these properties are discussed. Hysteresis properties are also reported. [Copyright &y& Elsevier]