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In present research, we employed sol-gel auto-combustion method to synthesize soft ferrites, specifically Ca 0.5 Co 0.5 Cr x Fe 2-x O 4 , with Cr3+ doping, where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5. As the Cr3+ concentration increased, we observed decrease in both the average crystallite size (from 16.4 nm to 13.5 nm) and lattice constant (form 8.3 Å to 8.2 Å). Notably, the Ca 0.5 Co 0.5 Cr 0.3 Fe 1.7 O 4 sample exhibited the highest AC conductivity at room temperature. Raman spectroscopy confirmed the presence of five active molecular vibrational modes, namely A 1g , E g, and 3T 2g. Direct current (DC) resistivity decreased with the increasing concentration of Cr3+, and the Ca 0.5 Co 0.5 Fe 2 O 4 sample displayed the maximum DC resistivity (6.81 × 108 ohm cm) at a Curie temperature of 383 K. Magnetic properties of soft ferrites, characterized through M-H loop analysis, revealed coercivity values in the range of H C = 1242.6 Oe to 660.8 Oe. These synthesized ferrites exhibit potential applications in longitudinal recording media owing to their performance in the microwave frequency range (6.0 GHz to 13 GHz), consistent DC resistivity, and stable dielectric constant. [Display omitted] • Ca 0.5 Co 0.5 Cr x Fe 2-x O 4 (0.0 ≤ x ≤ 0.5) ferrites were prepared by sol-gel auto combustion. • Dielectric factors exponentially decreased as a function of frequency. • The maximum ac conductivity was revealed by sample x = 0.3 at room temperature. • Maximum DC resistivity (6.8 × 108 Ω-cm) was shown by sample Ca 0.5 Co 0.5 Fe 2 O 4. • Microwave frequency range confirmed the ferrites are best for microwave devices. [ABSTRACT FROM AUTHOR]

Cadmium ferrites belong to normal spinel ferrites, and they exhibit interesting electrical, magnetic, and optical properties. The pure and cerium-doped cadmium ferrites CdFe2−xCexO4 (x = 0.0, 0.125, 0.250, 0.375, 0.5) were synthesized by a chemical co-precipitating technique using sodium hydroxide as a co-precipitating agent. The structures and phase purity of fabricated nanomaterials were analyzed by X-ray diffraction (XRD). The crystallite size for all the prepared nanomaterials was in the range of 28–46 nm. The lattice constant and unit cell volume were found to decrease with the increasing concentration of Cerium, which was confirmed by the peak shift in the XRD pattern. The X-ray density for all nano ferrites increased with the enhancement of cerium composition. The resistivity of the nanomaterials has random behavior with the enhancement of cerium composition for a temperature, but the value of resistivity at x = 0.125 has the lowest value and at x = 0.375 has the highest value for almost all temperatures. For specific concentrations, a decreasing trend of resistivity of fabricated materials was found with an increment of temperature. The activation energies were also calculated, and it increased for x = 0.125 and then decreased for all the nanomaterials. For the confirmation of the M–O bonds, FTIR analysis of all the nano ferrites was also performed. The analysis shows a higher frequency absorption band in the range of 531.24–534.84 cm−1. This absorption band confirms that metal oxides are formed in all the synthesized nanoparticles. [ABSTRACT FROM AUTHOR]

Cobalt ferrites have attracted extraordinary attention due to their high coercivity, chemical stability, and mechanical hardness. Lanthanum doped-cobalt ferrites having chemical formula CoLaxFe2-xO4 with composition x = (0.00, 0.015, 0.045, 0.060) were synthesized by chemical co-precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and current-voltage (I-V) technique. The structure of the crystal was analyzed by X-ray diffraction. The crystallite size of nanoparticles was examined in the range of 21–25 nm, and a fluctuating trend was found with the inclusion of La3+ cations. The X-ray diffraction patterns verify the contraction of lattice constant and unit cell volume with the substitution of La3+ cations except for the concentration of x = 0.060. Lattice constant was in the range of 8.34 Å–8.41 Å while unit volume cell was in the range of 580 Å3–596 Å3. The resistivity of all samples was calculated by the application of two probes I-V technique. The maximum resistivity of the order of 81.129 × 105 Ω cm was found for the concentration of x = 0.060 at 723 K which makes it useful for high-frequency gimmicks applications. The resistivity and drift mobility were found inversely related to each other. The inverse relation low-frequency absorption band and high-frequency absorption bands were analyzed by Fourier-transform infrared spectroscopy technique. [ABSTRACT FROM AUTHOR]

Due to their outstanding properties, low cost, and environmental friendliness, mixed transition metal oxides are frequently used in various applications. In this study, Ce3+ doped CdFe 2 O 4 powder samples were prepared through the co-precipitation process. A peak shift was observed towards a lower 2 θ angle with the substitution of Ce3+ at their lattice site and the lattice constant has a maximum value for the x = 0.06 sample with the crystallite size of 34 nm. Moreover, for x = 0.06 sample, the resistivity was found in the order of 106 Ω cm and the dielectric tangent loss had a smaller value. The electrical and dielectric analysis of the as-prepared x = 0.06 sample indicate that it is the best for high-frequency applications. • The Ce3+ doped CdFe 2 O 4 samples were prepared via the co-precipitation route. • The crystallite size was found 34 nm for a sample having Ce3+ x = 0.06 sample. • The x = 0.06 sample resistivity was observed in the order of 106 Ω cm. • The dielectric tangent loss has a smaller value for the x = 0.06 sample. • The electrical and dielectric properties suggested that x = 0.06 sample is suitable for high-frequency applications. [ABSTRACT FROM AUTHOR]

Transition metal vanadate nanostructures are getting significant importance as an efficient electrode material for modern energy storage applications. In this work, a simple hydrothermal method is employed for the synthesis of magnesium vanadate (MgV 2 O 5) and Ag-doped magnesium vanadate (Ag doped MgV 3 O 8) nanomaterials. The X-ray diffraction (XRD) analysis reveals the formation of an orthorhombic structure for magnesium vanadate, whereas the Ag-doped magnesium vanadate results in a monoclinic structure. Interestingly, the optical bandgap is observed to increase from 2.85 eV to 3.92 eV with the increase in Ag-doping as revealed from Tauc's plot of the UV-visible absorption spectrum. The electrochemical performance of magnesium vanadate electrodes is thoroughly investigated by cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy. The Ag-doped magnesium vanadate shows higher specific capacitance (C s = 706 Fg−1) in comparison to undoped (325 Fg−1) at a current density J = 5 Ag−1. The theoretical investigations through Dunn's model demonstrate a major contribution arises from surface-controlled processes, which increase as high as 91% at scan rate of 60 mVsec−1. Our findings indicate that Ag-doping significantly improves the overall electrochemical response of magnesium vanadate as an efficient electrode material for supercapacitor applications. [Display omitted] • Phase and lattice parameters of zinc vanadate are changed due to difference in ionic radii of dopant element (Ag). • Variable oxidation of states of vanadium are observed which cause improvement in electrochemical response. • Ag (2%) doped magnesium vanadate shows higher specific capacitance (Cs = 706 Fg−1) than undoped (325 Fg−1). • Silver-modified electrode exhibits energy density and power density of 65.5 Whkg−1 and 12,100 Wkg−1 respectively. [ABSTRACT FROM AUTHOR]

The impact of Cr3+ substitution on the electrical and dielectric properties of Y-type hexaferrites with composition Ba 2 Mg 2 Cr x Fe 12-x O 22 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) was synthesized by the sol-gel auto combustion technique. The lattice parameters 'a' and 'c' slightly increase with the substitution content of Cr3+, and some other physical parameters, including porosity, microstrain, dislocation density, specific surface area, and stacking fault coefficient, were determined from XRD data. FTIR spectra confirm the formation of iron oxide base material by the appearance of three signature bands at precisely 429, 474, and 499 cm-1 due to Fe–O vibrations at octahedral and tetrahedral sites. Substituting Cr3+ at the octahedral site enhanced the room temperature DC electrical resistivity from 6.89 × 109 to 2.27 × 1010 Ω-cm. Temperature-dependent DC electrical resistivity exhibits semiconducting behavior. There is a direct relation between resistivity and activation energy. The dielectric behavior of Cr3+ substituted samples in the frequency range of 1 MHz–6 GHz was understood based on the conduction mechanism through the hopping of electrons between Fe3+ and Fe2+ ions and the Maxwell-Wagner Model. In impedance spectroscopy studied using Cole-Cole plots, most dielectric response arises from the contribution of the grain boundary effect. With the substitution of Cr3+, dielectric losses decreased. A very high Q-value around 1 GHz was observed, suggesting that these hexaferrites are efficient materials for many high-frequency applications, such as multi-layer chip inductors (MLCI), dielectric resonators, and power applications. [ABSTRACT FROM AUTHOR]

This work studied a composite of graphene nanoplatelets (GNPs) impregnated copper-cobalt-samarium ferrites Cu 0.5 Co 0.5 Fe 1.97 Sm 0.03 O 4 /GNPs synthesized via sol-gel auto-combustion route. The structural, electrical, dielectric, and optical properties of the as-prepared composites were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), EDX, I-V characteristics, impedance measurement, raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) analysis, and UV–visible spectroscopy. XRD confirmed that the spinel ferrites had a crystalline single-phase FCC structure with the lattice constant of around 8.33 Å, and the crystallite size range from 54.10 nm to 51.85 nm. SEM analysis confirmed the homogenous dispersion of spinel ferrites in graphene sheets, and EDX confirmed the presence of all elements in ferrite composites with GNPs. Furthermore, the spinel matrix was confirmed by the Raman and UV-visible analysis. A minimum particle size of 21.73 nm was determined using TEM, and the minimum value of activation energy (0.01 eV) was obtained from IV characteristics for ferrite composite with 2.5% GNPs. Further, our ferrite composites with GNPs demonstrated improved electroconductive properties, with conductivity ranging from 5.88 × 10 − 8 S / cm to 1.04 × 10 − 6 S / cm at 673 K. The real & imaginary part of permittivity, dielectric constant (ε'), and impedance (Z) were also improved with the addition of GNPs. At low frequencies, a permeability loss value of 0.81 was obtained for the ferrite composite with 5% GNPs. VSM analysis confirmed that the saturation magnetization decreased in ferrite composites with graphene nanoplatelets. The minimum value of skin depth of 1.03 mm was observed at 1.25 % GNPs. Our ferrite composites with GNPs exhibited minimal eddy current at high frequencies, making them promising candidates for high-frequency device applications. [Display omitted] • The addition of graphene nanoplatelets (GNPs) increased the AC conductivity and reduced the impedance of synthesized composite of GNPs impregnated Copper-Cobalt spinel ferrite (GNPs-CCF Composite). • Graphene nanoplatelets decreased the optical bandgap of GNPs-CCF Composite. • A minimum activation energy (E a = 0.01 eV) was observed at a GNPs concentration of 2.5 %. • The addition of GNPs to the GNPs-CCF Composite has positioned the synthesized material as an excellent candidate for high-frequency device applications and microwave absorption. [ABSTRACT FROM AUTHOR]

Cadmium ferrites belong to normal spinel ferrites, and they exhibit interesting electrical, magnetic, and optical properties. The pure and cerium-doped cadmium ferrites CdFe2−xCexO4 (x = 0.0, 0.125, 0.250, 0.375, 0.5) were synthesized by a chemical co-precipitating technique using sodium hydroxide as a co-precipitating agent. The structures and phase purity of fabricated nanomaterials were analyzed by X-ray diffraction (XRD). The crystallite size for all the prepared nanomaterials was in the range of 28–46 nm. The lattice constant and unit cell volume were found to decrease with the increasing concentration of Cerium, which was confirmed by the peak shift in the XRD pattern. The X-ray density for all nano ferrites increased with the enhancement of cerium composition. The resistivity of the nanomaterials has random behavior with the enhancement of cerium composition for a temperature, but the value of resistivity at x = 0.125 has the lowest value and at x = 0.375 has the highest value for almost all temperatures. For specific concentrations, a decreasing trend of resistivity of fabricated materials was found with an increment of temperature. The activation energies were also calculated, and it increased for x = 0.125 and then decreased for all the nanomaterials. For the confirmation of the M–O bonds, FTIR analysis of all the nano ferrites was also performed. The analysis shows a higher frequency absorption band in the range of 531.24–534.84 cm−1. This absorption band confirms that metal oxides are formed in all the synthesized nanoparticles. [ABSTRACT FROM AUTHOR]

Z n 0.5 C o 0.25 C u 0.25 F e 2 − x L a x O 4 (x = 0.0, 0.0125, 0.025, 0.0375, 0.05) ferrite powders with uniform distribution of ions and close-packed configuration were prepared via sol-gel auto-combustion route. XRD spectra showed the formation of spinel-phase cubic crystalline structure. SEM results revealed that the irregularity in size and shape of particles increases, and particle distribution uniformity decreases with La3+ concentration. Moreover, each curve of the UV–vis spectra revealed two optical energy band gaps. More importantly, DC resistivity (ρ) and the activation energy (Δ E) have minimum values at x = 0.0375. The dielectric loss was explained according to Maxwell-Wager space charge polarization. The P-E loop showed the ferroelectric nature of the synthesized samples. Moreover, VSM results revealed that the as-prepared samples possessed maximum saturation magnetization (M S = 56.77 ± 0.0283) and 8–12 GHz operating microwave frequency (ω m) range at x = 0.0375. All these results show the potential of Z n 0.5 C o 0.25 C u 0.25 F e 1.9625 L a 0.0375 O 4 ferrite powders for X-band microwave applications. Image 1 • Zn 0.5 Co 0.25 Cu 0.25 Fe 2-x La x O 4 ferrite powders via simple sol-gel auto-combustion. • Crystallite size and lattice constant decrease with increasing La3+ cations. • Optical band gap energies and DC resistivity have minimum values at x = 0.0375. • The ferroelectric nature of all the samples was confirmed using the P-E loop. • Maximum magnetization saturation was observed at x = 0.0375. [ABSTRACT FROM AUTHOR]

Tertiary Cu 0.25 Ni 0.15 M 0.25 Co 0.35 La 0.15 Fe 1.85 O 4 (M = Mg 2+ , Mn 2+ , and Cd 2+ ) spinel ferrites powders were prepared using the cost-effective sol-gel auto combustion route. The lattice parameters, absorption and vibrational bands, energy band gap, AC conductivity, and dielectric loss of the as-prepared ferrites were all measured. The Cd2+ doped ferrite has a minimum crystallite size (D) of 50.9 nm, which is smaller compared to Mg2+ and Mn2+ doped ferrites. Furthermore, the X-ray diffraction (XRD), as well as Fourier transform infrared radiation (FTIR) and Raman analysis confirmed the doping of Mg2+, Mn2+, and Cd2+ ions on their respective lattice sites. The resistivity of the divalent ions (Mg2+, Mn2+, and Cd2+) doped ferrites decreased in the para region and increased in the ferro region as the temperature increased. Moreover, the resistivity of the Cd2+ doped ferrite was smaller when compared to the ferrites doped with Mg2+ and Mn2+ ions. From Arrhenius plots, the minimum activation energy (Δ E) 0.8671 eV was observed for Cd2+ doped ferrites. The Cd2+ substituted ferrite also has the smallest AC conductivity and dielectric loss compared to Mg2+ and Mn2+ substituted ferrites. The coercivity and saturation magnetization were 136.41 Oe and 92.29 emu/g for the Cd2+ doped ferrite, respectively. These results suggest that the Cd2+ doped ferrite material could be used in high-frequency and high-power applications. • The Cu 0.25 Ni 0.15 M 0.25 Co 0.35 La 0.15 Fe 1.85 O 4 (M = Mg 2+ , Mn 2+ , and Cd 2+ ) spinel ferrites were prepared. • Minimum activation energy and maximum optical bandgap energy were observed for Cd-CNCL ferrite. • The minimum coercivity and maximum initial permeability were found for Cd-doped CNCL ferrite. • The Cd2+ doped CNCL ferrite exhibits minimum dielectric losses. • The Cd2+ doped CNCL ferrite is best for high-frequency and high-power applications. [ABSTRACT FROM AUTHOR]