LiZn Ferrites Research Articles

The Influence of Additives on the Material Parameters of LiZn Ferrites

The effect of addition of CaO, Na2O, ZrO2, and Sb2O3 on some material parameters of sintered Li0.3Zn0.4Fe2.3O4 ferrite is described. The main purpose is to increase the density of the ferrite at low sintering temperature without compromising desirable material properties. By using additives an increase of the relative density from 94% to about 98.5% is achieved at low sintering temperature in order to avoid lithium and oxygen losses. Permeability, Curie point, and electrical resistivity are affected by additives. The influence of additives is explained both by their segregation at the grain boundaries and by their partial diffusion in the spinel lattice. Le présente travail montre l'effet de l'addition du CaO, Na2O, ZrO2 et Sb2O3 sur quelques paramètres de matériel du ferrite fritté Li0.3Zn0.4Fe2.3O4. Le principal but du travail est d'augmenter la densité du ferrite aux basses températures de frittage sans compromettre les propriétés désirées pour l'applications dans la haute fréquence. Par l'utilisation des additions on obtient un augmentation de la densité relative depuis 94% jusqu'a 98.5% aux basses températures de frittage ayant en vue d'éviter des pertes du lithium et d'oxygène. Nous trouvons que la perméabilité la temperature de Curie et la résistance électrique sont affectés par les additions. L'influence des additions est expliqué tant par leur ségrégation à la surface des cristaux que par leur partiel diffusion dans la réseau spinelle.

Li–Zn ferrites with nonmagnetic additives

AbstractThe authors investigated the effect of small additive amounts of non‐magnetic ions as Na1+, Ca2+, Zr2+, Sb3+ and binary or ternary combinations of these ions on some physical properties of the (Li0.5Fe0.5)0.6Zn0.4Fe2O4 ferrite used in high frequency. It was found that by the segregation of these additives on the grain boundaries, the grain growth is diminished and much higher sintered densities are obtained in several cases, though not all. We established that additives such as Na2O, CaO, ZrO2 enhance the rate of sintering, giving a speedy start to the sintering process. All additives improve the electrical resistivity due to insulating intergranular layers generated by segregation of additives.

Combustion synthesis and properties of fine particle Li-Zn ferrites

Lithium ferrites are attractive for microwave devices as a low-cost replacement for ferrimagnetic garnets [1, 2]. A serious problem with Li-Zn ferrite used in millimetre wave devices lies in poor densification. The pressure of porosity in Li ferrite samples enhances the insertion loss of the microwave device with increasing humidity. The porosity of ferrite manufactured by a conventional ceramic technique (with compositional inhomogeneity) is about 5-10% [3]. In order to attain better homogeneity and control over purity and particle size distribution, chemical routes involving metal formates [4, 5] have been used. Sintering aids such as $Bi_20 _3$ [6] or HIP have been studied for the preparation of high-den- sity materials. With HIP, under appropriate condi-tions the density of the bead material approaches X-ray density [7]. The density of magnetic ceramics depends on various factors, of which the reactivity and homogeneity of the ferrite powders are of special importance. The difficulty encountered when sintering Li ferrites is the volatilation of Li and Zn at temperatures above 1100°C. Thus, technological applications necessitate the preparation of highly reactive, pure, homogeneous Li ferrite powders which can be sintered to a fully dense ceramic body at 1000 °C with controlled grain growth and the desired magnetic properties. In continuation of our studies on spinel ferrites by a precursor method [8, 9], we recently reported a rapid combustion synthesis of spinel ferrites [10-12]. In this letter, we report the preparation and properties of $Li_{0.5}Zn_x$ $Fe_{2.5-x}O_4$ (where x = 0 - 1 . 0 ) and $Li_{0.325}Zn_{0.275}$ $Co_{0.075}$$Fe_{2.325}0_4$ by the combustion of lithium nitrate, zinc nitrate, iron (III) nitrate and oxalyl dihydrazide (ODH) at 350 °C in les than 5 min.

Microstructure studies on Ti4+- and Zr4+-substituted Li-Zn ferrites

XRD and microstructure studies were carried out on Ti4+ and Zr4+-substituted Li-Zn ferrites prepared by standard ceramic technique. All the ferrite compositions exhibit single phase formation. The lattice parametera increases linearly with the content of Zn2+Zr4+ and Zn2+Ti4+, which is attributed to the ionic volumes of the cations involved. With substitution by Zr4+ the average size decreases, while with substitution by Ti4+ the grain size increases. In both the series grain size varies with the composition. Excess substitution of Zr4+ (x>0·4) leads to the formation of secondary images and discontinuous grain growth. Both Zr4+ and Ti4+ compositions obey Kurtz theory.

Composition Dependence of the Elastic Moduli of Mixed Lithium—Zinc Ferrites

Mixed Li-Zn ferrites are prepared by the well-known double sintering ceramic technique. From the X-ray diffraction studies lattice parameters are calculated and their variation with composition is explained on the basis of the tetrahedral ionic radius. The bulk density of the specimens are determined by the hydrostatic method. The ultrasonic compressional (Vl) and shear (Vs) velocities of mixed Li-Zn ferrites are measured at room temperature using the ultrasonic pulse transmission technique. The elastic moduli of the specimens are computed and corrected to zero porosity. The variation of elastic moduli with composition is interpreted in terms of binding forces between the atoms.

Neutron diffraction study of the magnetism of Li-Zn ferrites

The magnetic structure of Li-Zn ferrites has been studied by powder neutron diffraction and magnetic measurement. Some spin-canting-based theories are adopted to explain the experimental results. No long-range ordered spin canting structure is found in our research range ( x = 0.0–0.6), but a short-range ordered spin canting is most likely present. The substitution of zinc into A-sites induces the spin canting in B-sites, while the A-site's moments remain aligned. The slight change of the ratio of effective superexchange constants δ (= J ' BB/ J ' AB) with the substitution is considered to be a factor corresponding to the magnetization behavior of Li-Zn ferrites.

Spin‐Canting Effect and Magnetic Moment of LiZn Ferrite

AbstractThe magnetic moment at 0 K of zinc‐substituted lithium ferrite is calculated, based on the spin‐canting model, for an accurate relationship between the moment and the substituent level of zinc. A modified computational plan is adopted in the calculation in contrast with those of recent publications so that a hitherto optimal fitting between the theory and experiment is realized. A generalization is also made to the case of double‐substituted LiTiZn ferrite.

A model calculation of the magnetic moment of Zn-substituted Li ferrite at 0 K

A model calculation of the spin-canting effect for Li-Zn ferrite is presented here to improve the existing calculations and to determine an accurate relationship between the magnetic moment at 0 K and the Zn substituent level. It is assumed that, although the B sublattice can be subdivided into two commensurate sublattices B' and B" regarding the spin orientations because of the spin-canting effect, the spin orientation is actually random at local sites. In contrast with previous calculations, the exchange integral ratio JAB/JBB in this paper is expressed in terms of correlated molecular-field coefficients. By self-consistent iterative computation, excellent agreement between the theory and the experimental results is realised, which the authors consider to be the best of those published.

Effect of Ti 4+ substitution on the hyperfine interactions in LiZn ferrites

57Fe Mössbauer investigations were made on the system Li 0.35+0.5 t Zn 0.3Ti t Fe 2.35−1.5 t O 4 (0.0≤ t≤1.2) at 300 K and 77 K. The effect of variation of Ti concentration on the various hyperfine interactions have been discussed. It is observed that for t≤0.6 the Mössbauer spectra show well defined Zeeman pattern. The spectra for t= 0.8 is relaxed while for t≥1.0 there is the existence of a central doublet along with the relaxed magnetic sextet. This anomalous behaviour of the Mössbauer spectra at high diamagnetic substitution and the origin of the central doublet have been discussed.

Hexagonal ferrite materials for phase shifter applications at millimeter wave frequencies

The effect of anisotropy field and saturation induction on phase shift at millimeter-wave frequencies has been examined for hexagonal ferrite materials. The analysis was done for both uniaxial and planar anisotropy at three particular frequencies of technological interest, 30, 60, and 90 GHz. The work was concerned primarily with materials; a simple thin slab device configuration was used for the analysis. Limitations on materials parameters due to propagation cutoff, phase error degradation over a specified bandwidth, and low field loss were also considered. The results indicate that any improvement in phase shift over conventional cubic ferrites will require a high saturation magnetization, comparable to that of Li-Zn ferrite, and moderate (6-10-kOe) to large (20-30-kOe) anisotropy fields, depending on the frequency. >

Effective linewidth measurements at 36 GHz in hexagonal and cubic ferrites

Effective linewidth measurements at 36 GHz are reported for barium ferrite, several W-type single-crystal hexagonal ferrites, and for polycrystalline LiZn ferrite. In general, the effective linewidths for the W-type ferrites were relatively large—several hundred oersteds. Values of ΔHeff for the barium ferrite samples were tens of oersteds, similar to the ferromagnetic resonance (FMR) linewidths for these materials. The LiZn samples showed effective linewidths significantly below the FMR values. The results indicate that the two-magnon loss mechanism is the predominant factor in the polycrystalline LiZn, but contributes little to the ferromagnetic loss in single-crystal barium ferrite. The data for the W-type ferrites show that the intrinsic loss for these single-crystals is a significant part of the ferromagnetic resonance linewidth.

Spin wave stiffness constants in some ferrimagnetics

The magnitude of the spin wave stiffness parameter. D and its dependence on temperature in YIG, Fe3O4 and Li-Zn ferrite has been examined and compared with theory. It is shown that values of D obtained using the exchange constants that satisfactorily explain the equilibrium magnetic properties of these systems yield results in agreement with experiment for YIG and Fe3O4 but are inappropriate for the Li-Zn ferrite. The temperature dependence of D in YIG and Fe3O4 is satisfactorily explained on the basis of the interaction of acoustic magnons with optic magnons.

Neutron Diffraction Studies of the Magnetic Ground State in LiZn Ferrite

The magnetic structure of diamagnetically replaced LiZn ferrites with Zn content c = 0.5 to 0.9 is studied by neutron diffraction within the temperature range 1.8 to 10 K. It is shown that for 0.5 < c < 0.8 the ground state is a noncollinear magnetic structure, where Z components of the spin are ferrimagnetically aligned along the star K1 = 0 and the X−Y projections antiferromagneti-cally aligned along the star K2 = 2π/a {1/2 1/2 0}. For 0.8 ≦ C < 1 the ground state is an inhomo-geneous in space magnetic structure with finite ferrimagnetic and antiferrimagnetic spin correlation radii. Mittels Neutronenbeugung im Temperaturbereich von 1,8 bis 10 K wird die magnetische Struktur von diamagnetisch ersetzten Li-Zn-Ferriten mit einem Zn-Gehalt von c = 0,5 bis 0,9 untersucht. Es wird gezeigt, das fur 0,5 < c < 0,8 der Grundzustand eine nichtkollineare magnetische Struk-tur ist, wobei die Z-Komponente des Spins ferrimagnetisch in Richtung des Sterns K1 = 0 und die X−Y-Projektionen antiferromagnetisch in Richtung des Sterns K2 = 2π/a {1/2 1/2 0} ange-ordnet sind. Fur 0,8 ≦ c < l ist der Grundzustand eine im Raum inhomogene magnetische Struktur mit endlichen ferrimagnetischen und antiferrimagnetischen Spin-Korrelationsradien.

Brilliouin light scattering determination of the spin-wave stiffness parameter in lithium-zinc ferrite

The spin-wave stiffness parameter for Zn substituted Li-ferrite has been measured by the technique of Brillouin light scattering. A range of compositions from pure Li-ferrite through Li-Zn ferrite with 0.65 Zn at./formula unit was studied. The magnon frequency vs. field determinations from light scattering and separate magnetization data were used to determine the spin-wave stiffness parameter, D. The data give a D-value of 10.1 × 10-9Oe.cm2for pure lithium ferrite, approximately twice as large as for yttrium iron garnet. A rapid decrease occurs with Zn substitution and D is essentially zero for about 0.4 Zn at./formula unit. These are the first reported results of Brillouin scattering from a polycrystalline ferrite. A molecular field calculation of the spin-wave stiffness yields a much slower decrease in D with zinc than is found experimentally.

Low temperature sintering of Mg-Mn-Zn ferrites

A method to lower sintering temperature of ferrites was studied. It was found that the sintering temperature could be reduced remarkably by means of both substitution of lithium and addition of lithium borosilicate glasses to Mg-Mn-Zn ferrites, which is used for television deflection yokes. For example, when lithium borosilicate glass containing 20 mol% Li <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O, 40 mol% B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> and 40 mol% SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> is added to lithium substituted Mg-Mn-Zn ferrite with a composition of Mg <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.64</inf> Mn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.06</inf> Li <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.04</inf> Zn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.23</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.03</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.99</inf> ,the sintering temperature decreases by 200°C as compared with that of Mg-Mn-Zn ferrite. Particularly, Li-Zn ferrite with addition of this glass can be sintered at 800°C. In ferrites prepared by liquid phase sintering, the magnetic properties often become worse, but with this method, the properties remain almost the same as those of the mother ferrites.

Anomalous behaviour of cobalt in soft lithium-zinc ferrites

In regard to the magnetic anisotropy, Co does not act on permeability of Li-Zn ferrites like it does in pure Li and in Li-Ga ferrites. This result is being tentatively explained by assuming a reduction of Co anisotropy due to canting of the Co moments, since such a canting was found to modify the anisotropy of Fe 3+ ions in Li-Zn ferrites.

Cation distribution in substituted lithium ferrite

Magnetization data are not sufficient for a comprehensive understanding of cation distribution of substituted Li ferrites. Neutron and X-rays diffraction, and Mossbauer experiments were carried out on several Li-Zn and Li-Ti ferrites with general compositions : Fe 2.5-z/2-3t/2-m Li 0.5+t/2-z/2 Zn z Ti t Mn m O 4 (0 < z < 0.7, 0 < t < 0.8, m is either 0 or 0.035). The agreement between Mossbauer, magnetic, X-ray and neutron data give a difinitive answer about the distribution of Zn and Ti substituted lithium ferrites.

Resistivity and Curie Point of Li‐Zn Ferrites

Journal of the American Ceramic SocietyVolume 57, Issue 1 p. 40-40 Resistivity and Curie Point of Li-Zn Ferrites N. REZLESCU, N. REZLESCU Research Center of Physics, Jassy, Romania.Search for more papers by this authorD. CONDURACHE, D. CONDURACHE Research Center of Physics, Jassy, Romania.Search for more papers by this authorP. PETRARIU, P. PETRARIU Research Center of Physics, Jassy, Romania.Search for more papers by this authorE. LUCA, E. LUCA Research Center of Physics, Jassy, Romania.Search for more papers by this author N. REZLESCU, N. REZLESCU Research Center of Physics, Jassy, Romania.Search for more papers by this authorD. CONDURACHE, D. CONDURACHE Research Center of Physics, Jassy, Romania.Search for more papers by this authorP. PETRARIU, P. PETRARIU Research Center of Physics, Jassy, Romania.Search for more papers by this authorE. LUCA, E. LUCA Research Center of Physics, Jassy, Romania.Search for more papers by this author First published: January 1974 https://doi.org/10.1111/j.1151-2916.1974.tb11360.xCitations: 36AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume57, Issue1January 1974Pages 40-40 RelatedInformation