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Sol–gel technique is utilized to produce the series of ferrite having chemical formula BaYyFe2-yO4 (y = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10). The cubic structure of all the samples have been revealed through X-ray diffraction data. The inclusion of yttrium content among the ferrites beyond 0.06, it will result into development of YFeO3 secondary phase. The lattice parameter of samples upsurges with the substitution of yttrium ions (Y3+). Jump lengths on A & B sites, bond lengths and ionic radii have direct relation with yttrium concentration. The evaluation of electrical parameters reveal that the resistivity, activation energy and bond length increased with the growth of yttrium. Below the Curie temperature, the movement of electrons and holes is main cause of conduction mechanism. But above this temperature, the polaron hopping handle the conduction process. With the addition of yttrium, the saturation magnetization value decreased. Coercivity of samples enlarged with the substitution of yttrium ions. The involvement of yttrium ion in barium ferrite system makes it appropriate for high frequency appliances.

The rare earth (Yb3+) substituted W-type hexagonal ferrites with composition CaPb 2-x Yb x Fe 16 O 27 (x = 0.0, 0.5, 1.0, 1.5, 2.0) were synthesized by a facile and cost-effective sol-gel auto combustion method with post heat treatment. The synthesized hexagonal ferrites were characterized by a variety of analytical techniques, and an impedance analyzer was used to investigate the effects of Ytterbium on structural, magnetic, spectral and dielectric properties. The relationship between their impedance, structure and dielectric properties was investigated. The X-ray diffraction patterns verify the presence of single-phase W-type hexagonal ferrites. Physical properties such as D bulk (bulk density), D xrd (X-ray density), and P (porosity) of the CaPb 2-x Yb x Fe 16 O 27 W-type hexagonal ferrites were calculated. The bulk density of all the samples was decreased, and X-ray intensity was increased with the Ytterbium replacement in the W-type hexaferrite. By adding Yb3+ ions, the lattice parameters, cell volume and X-ray density were reduced due to the substitution of ytterbium with smaller ionic radii compared to the lead ion with large ionic radii. The AC-conductivity was increased from (1.523 × 10−5 to 6.699 × 10−5) Ωcm−1. The dielectric constant and tangent loss was found to decrease substantially. The magnetic properties were found to enhance by the substitution of Yb3+. The low coercivity value of Yb3+ substituted W-type hexagonal ferrites are suitable for magnetic recording media operated at a high-frequency regime. The enhancement of electrical, dielectric and magnetic characteristics suggests these materials as promising for multi-layer chip inductors (MLCIs) circuit applications. [ABSTRACT FROM AUTHOR]

Sol-gel auto combustion was used to create a sequence of soft ferrites, NixMg1-xFe1.9Sm0.1O4(x = 0.0, 0.2, 0.4 & 0.6). The XRD, FTIR, UV-vis, & four probe I-V techniques, respectively, were used to evaluate the structural, optical, and electrical properties. The cubic crystal structure was confirmed by the XRD pattern. The range of 25.71 - 33.67 nm was found to be the average crystallite size. FTIR spectra provided evidence of the tetrahedral band's existence. With the enhancement of Ni2+ concentration, Eg was determined from 2.28-3.21 eV. It was confirmed by the ranges of DC electrical resistivity that materials might be used in transformers to lessen eddy current losses. [ABSTRACT FROM AUTHOR]

In this work, sol-gel auto-combustion technique was employed to synthesize Pb2Co2-xNixFe28O46(x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2) X-type hexagonal ferrites. Annealing of the samples was done at 1050 °C for 10 h. Formation of the X-type hexaferrites phase was confirmed by the XRD technique. Scanning electron microscopy was used to observe the morphology of the prepared samples. Crystallite size ranges from 15.40 to 10.10 nm. The unit cell volume was measured in the range of (2497.5-2514.1) Å . The cell volume and the lattice constants changed due to the difference in radii of the base and doping element. Distortion parameter (g) and dislocation density (δ) varied directly to site vacancies in the layers and the reordering of the lattice atoms during the transformation process. FTIR spectrum revealed the presence of particular absorption bands (metal-oxygen stretching vibration) which also confirmed the formation of hexagonal ferrites, and it was recorded in the range 600-4000 cm - 1 . Dielectric parameters exhibit frequency-dependent behavior. The dielectric constant (ɛ′), dielectric loss (ɛ″), and tan loss (tanδ) decreased abruptly at low frequency and then remained invariant up to 1.5 MHz. The higher values of the dielectric parameters recommend fabricated material a potential candidate for high-frequency applications. Dielectric constant and Q-value were found to increase with the increase in Ni content. All the samples revealed resonance peaks above 1.9 GHz which indicates the potential use of the material for EMI attenuation. The optimized dielectric nature of the prepared hexaferrites suggests the material to be useful in the manufacturing of multilayer chip inductors (MLCIs). [ABSTRACT FROM AUTHOR]

A series of rare earth elements (RE = Ce, Dy, Yb, La and Pr) substituted Sr0.9RE0.1Mn2Fe4O11 R-type hexagonal ferrites has been prepared by using the Sol–gel technique. The effect of RE substitution on its structural, electric polarization, dielectric and microwave absorption properties was studied. XRD patterns showed that all the prepared samples possess R-type hexagonal structure. The lattice parameters and unit cell volume varied with the substitution of RE contents. The average crystallite size, measured by Scherer formula, varied in the range of 6–15 nm for all samples. These results make this material suitable for being used in multilayer chip inductors (MLCI's). The dielectric constant was found to decrease at high frequencies. This behavior has been explained on the basis of Maxwell–Wagner's and Koop's theory. An increase in AC conductivity was observed with increase in frequency. The decrease in lossy behavior with RE substitution in pure sample indicated the increase in the resistive nature of samples as observed from the electric polarization analysis. The Yb substituted sample exhibited highest value of microwave absorption − 40.5 dB at 11.4 GHz frequency among all the substituted samples. [ABSTRACT FROM AUTHOR]

The x-type hexaferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized crystal X-type hexagonal ferrites is still a big challenge. Herein, the synthesis of nanosized X-type hexagonal ferrites Ca 2 Co 2−x Zn x Fe 28 O 46 (X = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0) with high quality is reported using the auto-combustion sol-gel method. The objective of the study was to improve the structural and dielectric properties of X-type hexagonal ferrite which was achieved through variation of concentration of cobalt and zinc. Structural, morphological, and dielectric properties were investigated. X-ray diffraction (XRD) patterns confirmed the single-phase x-type hexagonal structure. The crystal size of all samples was in the range of 22.7–23.8 nm. Other parameters such as d -spacing, lattice parameters, unit cell volume, dislocation density, atomic packing fraction, degree of crystal lattice distortion, number of the unit cells, and volume of particles were also calculated. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of metal oxide bonds with two absorption bands at 574 cm−1 and 424 cm−1. The morphology of the prepared Ca 2 Co 2−x Zn x Fe 28 O 46 with the variation of Co and Zn was examined by scanning electron microscopy. Increasing crystallinity and agglomeration were observed with the upsurge in Zn and Co. The dielectric properties of Ca 2 Co 2−x Zn x Fe 28 O 46 with the variation of Zn and Co revealed that these materials might be considered good candidates for modern devices. [Display omitted] • Nanosized X-type hexagonal ferrites was synthesized by auto-combustion sol-gel. • Crystal size of all samples was in the range of 22.7–23.8 nm. • Dielectric properties revealed that materials are good candidate for devices. [ABSTRACT FROM AUTHOR]

Abstract: Effect of Pr–Ni substitution on structural and magnetic properties of Ca0.5Ba0.5−x Pr x Ni y Fe12−y O19 (x=0.00–0.10 and y=0.00–1.00) prepared by the sol–gel auto combustion method were investigated. The XRD analysis confirmed the single phase M-type hexa-ferrite structure. The lattice parameters were found to increase as Pr–Ni content increases, which is attributed to the ionic size of the implicated cations. The Pr–Ni seems to be completely soluble in the lattice. Transmission electron microscopy reveals that the grain size decreases with increase of Pr–Ni substitution. The coercivity and remanent magnetization ranges from 1511 to 1925 (Oe) and 21.4 to 26.5 (emu/g), respectively. The coercivity values of all the samples fall in the range of M-type hexa-ferrites. [Copyright &y& Elsevier]

Highlights: [•] Tb–Zn substituted Ca0.5Ba0.5Fe12O19 samples exhibit single magnetoplumbite phase. [•] Lattice parameters a and c have increasing values. [•] Coercivity can be tuned at lower substitution level [•] Crystallites size was found in the range 18–25nm by TEM and by Scherrer formula. [•] These hexa-ferrites are suitable for microwave devices and magnetic recording media. [Copyright &y& Elsevier]

We investigated electrical properties of nanostructured LaSrFeO (0 ≤ x ≤ 1) from 300 K-400 K. The nanostructured LaSrFeO (0 ≤ x ≤ 1) was synthesized by citrate gel method requiring no pH control. X-ray diffraction pattern showed that single phase LaFeO with an orthorhombic structure was formed. The structure changed into rhombohedral for x = 0.5 and it became cubic for x = 1.0. For x ≤ 0.5, our material showed non-linear current-voltage characteristics and for x > 0.5 it showed linear current-voltage characteristics. Poole Frenkel type conduction mechanism was found to be operative in LaFeO from 300 K-400 K. The experimental values of field-lowering coefficient were by 2.56-6.41 times higher than the predicted value and were attributed to the presence of localized fields. The increase in conductance with Sr content was due to formation of Fe ions in addition to Fe with the increase in Sr content. Impedance spectroscopy and ac conductivity analysis of LaSrFeO (0 ≤ x ≤ 1) was also carried out in the temperature range from 300 K-400 K and frequency was varied from 20 Hz - 2 MHz. The ac conduction followed the correlated barrier hopping model in LaSrFeO. [ABSTRACT FROM AUTHOR]

A series of W-type Ba-based Co-W ferrites with composition BaCoxCd2-xFe16O27 (x - 0.0, 0.1, 0.2, 0.3, 0.4 & 0.5) were fabricated by co-precipitation process at sintering 1100 °C for 8 h. In order to investigate structural, optical, electrical and magnetic properties XRD, FTIR, IV and VSM tools were employed to confirm the formation of ferrites phase. Crystallite size was observed in the range of 71.79 - 27.88 nm with the increase of cobalt contents to confirm the formation of W-type phase. FTIR investigated the existence of metal oxide (M - O). Electrical resistivity increased in the range of 0.2315 x 107 - 0.5329 x 107 ohm.cm. Saturation magnetization (Ms) of the synthesized sample were observed in the range (37.36 emu/g to 87.42 emu/g) and remanance (Mr) found (2.21 emu/g to 27.81 emu/g) while coercivity (Hc) observed in the range (42.58 Oe to 346.55 Oe). Explored results revealed that such type of behavior by material is suitable for application of magnetic recording media. [ABSTRACT FROM AUTHOR]

A series W-type BaMe2Fe16O27 ferrites withcomposition BaZnxCo1-xFe16O27(x - 0.0, 0.1, 0.2, 0.3, 0.4 &0.5) were manufactured by co-precipitation method sintering at 1100°C for 8 h. XRD, FTIR, SEM, UV-vis and I-V techniques were applied to investigate structural, optical, morphological and electrical properties respectively. Crystallite size was observed in the range of (37.58 nm-54.75 nm) revealed by XRD and was confirmed by SEM analysis. IR exposed the existence of metal oxides (M-O). Optical band gap was in (3.0 eV-5.2 eV) range which proved the trend of DC resistivity in increasing trend. Activation energy discovered the conversion of ferrimagnetism to paramagnetism characteristics confirming the W-type materials are highly suitable for novel application. [ABSTRACT FROM AUTHOR]

Holmium (Ho 3+ ) substituted W-type hexagonal ferrites (BaCo 2 Fe 16 O 27 ) were prepared by sol gel auto-combustion technique. The precursors were prepared by Ba 2+ , Fe 3+ nitrates solutions with citric acid as chelating agent. The prepared powder was sintered at 950 °C for 8 h to produce a single phase of W-type hexa ferrite with corresponding crystallite size ranging from 34 nm to 44 nm. The thermal decomposition of nitrate-citrate gel of as-prepared powder was investigated by TGA and DTA. The FTIR spectral study reveals the presence of two absorption bands which are characteristics of hexaferrites. DC electrical resistivity increases from 3.01×10 9 to 5.69×10 10 (ohm-cm). The real and imaginary parts of dielectric constant (ɛʹ, ϵ״) and dielectric loss tangent (tan δ) are determined in the frequency range of 20 Hz–1 MHz. It was observed that both real and imaginary parts of the dielectric constant and tanδ decrease with the increase of frequency on the basis of Wagner and Koop's theory. [ABSTRACT FROM AUTHOR]

Y-type hexa-ferrite Sr 1.8 Sm 0.2 Co 2 Ni 1.50 Fe 10.50 O 22 was synthesized via micro-emulsion route. Ferrite/PST composites were obtained by mixing the different ferrite ratio in the pure PST matrix. The microstructure was examined by scanning electron microscopy (SEM) and exhibited heterogonous distribution of grains. A keen observation of these SEM images revealed that the grain morphology changes noticeably with increasing ferrite filler contents. The electrical modulus, Cole–Cole plots and quality factor of ferrite polymer composites have been investigated in the frequency range (1 MHz to 3 GHz). The field dependent magnetic properties of the prepared samples were investigated at room temperature by using vibrating sample magnetometer (VSM). The shape of hysteresis loops and linearity of M s , M r , H c values vs. ferrite contents unfold that the ferrite nanoparticles are evenly dispersed within the composite. The occurrence of resonance at high frequency suggests that the present investigated composite samples are best candidate for multilayer chip inductors. [ABSTRACT FROM AUTHOR]

Polycrystalline ferrites with chemical formula MgY 2 x Fe 2−2 x O 4 ( x =0.0 to 0.12) have been fabricated by a double sintering ceramic technique. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Impedance spectroscopy and Fourier transform infrared (FTIR) spectroscopy. A slight increase in lattice constant is observed for x =0.02 and thereafter it decreased for higher Y-contents. The increase in lattice constant is attributed to the difference in ionic radii of the cations involved and decrease led to the formation of secondary phase (YFeO 3 ). The substitution of yttrium impedes the grain growth. The resistivity at 298 K was significantly enhanced as the Y 3+ was increased. The FTIR band positions in the range of 370–1100 cm −1 exhibited two main absorption bands. These bands confirmed the completion of solid state reaction. As the Yttrium contents were increased the dielectric parameters were greatly influenced. Both the observed/optimized electrical and dielectric parameters suggested the potential use of the Y-doped MgFe 2 O 4 ferrites in high frequency devices fabrication. [ABSTRACT FROM AUTHOR]

Highlights: [•] The decreasing trend of saturation magnetization is attributed to the weakening of exchange interactions. [•] The change in lattice constant at x >0.04 indicated the solubility limit of Gd in the spinel lattice. [•] The high coercive Li–Mg ferrites may be suitable for high frequency microwave absorption. [Copyright &y& Elsevier]

Abstract: Eu substituted MnZn-ferrites with nominal composition Mn0.78Zn0.22Eu x Fe(2−x)O4 (x=0.0, 0.02, 0.04, 0.06, 0.08 and 0.10) were prepared by co-precipitation technique. The effect of Europium substitution on electrical transport properties of Mn–Zn ferrites is reported. XRD analysis reveals fcc phase in all the samples along with few traces of second phase. The lattice constant shows decreasing trend with the substitution of Eu due to partial solubility of Eu-ions in the lattice. Room temperature resistivity both at 10 and 20V shows on average an increasing trend. This increase in resistivity is attributed to the unavailability of Fe+3 ions in the lattice due to Eu-substitution. The dc resistivity decreases with temperature for all the samples at 10V and 20V indicating the semiconducting behavior of these samples. Room temperature dc resistivity and activation energies show similar trend both at 10V and 20V indicating that the samples with high resistivity have high activation energies and vice versa. The dielectric constant (ε′), complex dielectric constant (ε″) and loss tangent of these samples decreased with the increase of Eu-concentration, following the Maxwell–Weigner model. [Copyright &y& Elsevier]