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Ferrites are among the most frequently investigated materials mainly due to interesting and practically different properties. Therefore, easily and cost-effective lanthanum doped Mg 0.5 Cd 0.25 Cu 0.25 Fe 2-x La x O 4 (x = 0.0, 0.0125, 0.025, 0.0375 and 0.05) ferrites were synthesized by a co-precipitation route, a comprehensive characterisation of their structural, optical, electric, dielectric, molecular vibrational, and magnetic properties were carried out. X-ray diffraction analysis confirmed the formation of a cubic spinel structure. Variations in frequency bands were also observed with amplification in optical band gap energy (2.95 – 3.38 eV) due to La3+ ions insertion. The electric resistivity had opposite trends at low and high temperatures with increasing La3+ content. The Curie temperature, activation energy, and drift mobility were also determined to have values consistent with the semiconducting behavior of the soft ferrites. The saturation magnetization (M S) has a maximum value 49.385 emu/g with remanent magnetization (M r) was 34.928 emu/g and coercivity 661.4 Oe for La3+ concentration x = 0.05. The minimum dielectric loss was observed for La3+ concentration x = 0.025. Moreover, the resistivity (ρ) has a maximum value of 7.95 × 104 Ω cm for La3+ concentration x = 0.025. The calculated frequency range of La3+ doped Mg–Cd–Cu ferrites was detected in the microwave range (3.36 – 10.80 GHz), suggesting the potential application of the materials in longitudinal recording media and microwave absorbance. [Display omitted] • La3+ doped Mg–Cd–Cu ferritessamples synthesized via co-precipitation. • The lattice constant increased with La3+ substitution. • At 303 K, for La3+ concentration x = 0.025, maximum resistivity was observed. • Magnetization saturation was increased with La3+ concentration. [ABSTRACT FROM AUTHOR]

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]

The nanoparticle spinel ferrites Mg0.5Zn0.5CexLaxFe2-2xO4 (x = 0.0, 0.0125, 0.025, 0.0375, 0.05) were synthesized by mean of co-precipitation method. These magnetic nanoparticles were sintered at 750 °C for 8 h. XRD patterns confirmed the formation of the cubic spinel structure of prepared nanoparticles. The lattice constant of nanoparticle ferrites increased, while crystallite size decreased with doping content (x). Pure ferrite sample has an optical bandgap of 2.61 eV, and it increases from 1.73 to 2.17 eV as concentration (x) is changed from 0.0125 to 0.05. The electrical dc resistivity is of the order of 1010 Ω cm for doping content (x) from 0 to 0.0375 and has a maximum value of 5.48617 × 1012 Ω cm for content x = 0.05. The Curie temperature (Tc) decreased 433–373 K as concentration (x) was increased. The dielectric constant, dielectric loss, and impedance are reduced with the increase of frequency. The dielectric constant, as well as the dielectric loss diminished while impedance increased as doping of cerium and lanthanum, was increased. [ABSTRACT FROM AUTHOR]

Cost-effective and controllable synthesis of M0.25Ni0.15Cu0.25Co0.35Fe2O4 (M2+ = Mg2+, Mn2+, and Cd2+) ferrites via the sol–gel auto-combustion technique. The impact of divalent cations on the structural, dielectric, and optoelectrical properties of ferrites was examined by XRD, FTIR, Raman, LCR, UV–Vis, and two probe I-V measurement techniques. The crystallite size was 52.66 nm, and the minimum specific surface area was observed 5.1507 m2/g for Mg2+ doped NCCF ferrite. The FTIR and Raman analysis also confirmed the substitution of divalent cations (M2+ = Mg2+, Mn2+, and Cd2+) at their respective lattice sites. The maximum energy bandgap was 1.67 eV Mg2+-doped NCCF ferrite as compared to other divalent ion-doped ferrites. The dielectric loss decreased while the ac conductivity increased with increasing frequency, and the minimum values were observed for Mg2+-doped NCCF ferrite. The activation energy was observed maximum for Mg2+-doped NCCF ferrite (0.2234 eV). Due to incredible properties including small specific surface area, large energy band gap, high resistivity, and loss dielectric loss of Mg2+-doped NCCF ferrite have potential applications in different fields. [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]

Low temperature and more efficient sol-gel auto combustion process was utilized to synthesize Co 0.3 Li 0.1 Ca 0.5 Fe 2.1- x La x O 4 [ La-CLCF ] spinel ferrites (where x = 0.00, 0.01, 0.02, 0.03, 0.04, and,0.05). The La-CLCF sample's structural, optoelectrical, dielectric, and magnetic properties were examined as a result of La3+ doping. All synthesized La-CLCF samples have single-phased spinel matrix, according to X-ray diffraction (XRD) analysis. It was found that the crystallite size was 11 nm, and the bandgap energy of 3.45 eV for La3+ doping x = 0.03. The resistivity and activation energy both were increased with the substitution of La3+ in the CLCF spinel matrix, while the peak position of temperature coefficient of resistance (TCR) percentage was − 3.92%/K at 372 K for sample x = 0.03. The alternating current conductivity improves with frequency, whereas the dielectric constant and tangent loss decrease as frequency increases. Further, the saturation magnetization and the microwave operating frequency for all the samples were reduced with the doping of La3+. The minimum coercivity was 242 Oe at x = 0.03. Our study suggested that the Co 0.3 Li 0.1 Ca 0.5 Fe 2.07 La 0.03 O 4 sample is tested as an active material for potential use in high-frequency applications, electromagnetic wave absorbing material, and evaluating the sensitivity of infrared (IR) detectors used in night vision bolometers. [Display omitted] • Co 0.3 Li 0.1 Ca 0.5 Fe 2.1- x La x O 4 spinel ferrites preparation via SGAC route. • The peak position of TCR was − 3.92%/K at 372 K for sample x = 0.03. • The minimum coercivity was 242 Oe for La3+ doping x = 0.03 • The sample x = 0.03 is a potential candidate for high-frequency applications, electromagnetic wave absorbing material, and bolometers. [ABSTRACT FROM AUTHOR]

This research work analyzes the impact of graphene nanoplatelets (GNPs) on the structural, electrical, dielectric, optical, and magnetic properties of the Ni 0·4 Cd 0·6 Fe 1.97 Sm 0.03 O 4 /x-GNPs (SNCF/GNPs) composites (x = 0 %, 2.5 %, and 5 %) prepared via the sol-gel auto-combustion route. The results revealed that SNCF particles were distributed on GNPs which improved the multifaceted properties of SNCF spinel ferrites. XRD analysis confirmed the FCC spinel structure with a minimum crystallite size (D) of 18.99 nm for sample with 5 wt %GNPs. The DC electrical resistivity decreased from 9.06 × 1011 Ω-cm at 313K to 1.41 × 108 Ω-cm at 673K, revealing the semi-conducting nature of composites. The improved electroconductivity and reduced bandgap energy are observed for samples with minimum resistivity 1.02 × 105 Ω-cm at 673K and 1.70 eV energy, respectively, containing 5 wt %GNPs. Samples show higher permittivity values at low frequency and decreased at high frequency. The maximum ac conductivity is observed for composite with 5 wt %GNPs which is attributed to the hopping mechanism. Finally, the magnetization (Ms) increased from 52.24 to 79.71 emu/g with increasing GNPs contents. Hence, the synthesized composites with 5 wt %GNPs are more favorable than the pure sample for application in waste-water treatment, high-frequency devices, and energy storage devices. • Samarium doped nickel-cadmium spinel ferrites (SNCF)/Graphene nanoplatelets (GNP) composites were successfully synthesized. • XRD analysis revealed the existence of FCC spinel structure in the SNCF/GNPs composites. • The direct band-gap energy of the SNCF/GNPs composites was found in the range of 1.70–1.78 eV. • Improved electrical, dielectric and magnetic properties of prepared composites. • Potential for various applications like wastewater treatment, high frequency devices and energy storage devices. [ABSTRACT FROM AUTHOR]

Rare earth cerium (Ce3+) doped Cu 0. 5 Cd 0. 25 Co 0.25 Ce x Fe 2-x O 4 (x = 0, 0.0125, 0.025, 0.0375, 0.05) spinel ferrites nanoparticles were synthesized via co-precipitation technique. XRD, FT-IR, UV-VIS, VSM, LCR and current-voltage measurement techniques were utilized to investigate the structural parameters, metal stretching vibrations, indirect energy band gap, magnetic parameters and electrical behavior of synthesized ferrite powders respectively. The XRD patterns confirmed the remarkable reduction in crystallites size, cell volume and lattice constant while both densities (ρ x , ρ b u l k ) tends to increase with rise in Ce3+contents(x). The indirect energy band gaps (E g) and the DC electrical resistivities were found in decreasing order from 3.48 to 2.50 eV and 9.902 × 107 to 0.142 × 107(ohm-cm) respectively at room temperature (303 K) with Ce3+ doping concentration. LCR meter inveterate that the dielectric constant had declining, and ac conductivity had growing trend at fix value of cerium concentration with rise of frequency from 8 Hz to 8 MHz. The soft magnetic properties can be significantly improved by the small amount of Ce3+ ion doping (x = 0.0375) with an increase of the saturation magnetization (Ms), and retentivity (Mr). [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]

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]

A series of (Zr–Co) substituted Y-type polycrystalline hexaferrite with composition SrBaNi 2 (ZrCo) x Fe 12-2x O 22 (x = 0.0, 0.25, 0.50, 0.75, 1.0) were fabricated by sol-gel auto combustion method. Pure Y-type single phase formation was achieved at a relatively lower temperature of 1150 °C for 5:30 h. The fabricated nano ferrites were examined by X-ray powder diffraction to confirm the pure single-phase formation of Y-type hexaferrites. An increase in lattice parameters (a& c) was observed by adding Zr4+-Co2+ metal cations. Crystallite size (D) measured in the 48-19 nm range. FTIR spectra clarified iron-oxygen vibrational bands at 417-487 cm−1, which approved the Y-type hexaferrites formation. DC electrical resistivity has an opposite trend at high and low temperatures with increasing Zr4+-Co2+ content (x). DC electrical resistivity values depend on grain size; they have an inverse relation. Activation energy, drift mobility, and Curie temperature were also determined. Conduction is due to the hopping of electrons below the Curie temperature, and polarons are responsible for hopping above the Curie temperature. Activation energy varies from 0.39 to 0.10 eV with the substitution of Zr4+-Co2+ ions. A wide frequency range of dielectric characteristics (1 MHz–6GHz) was observed, and these parameters revealed a considerable fluctuation with the substitution of Zr4+–Co2+ ions. Dielectric constant, dielectric loss and ac conductivity of nano ferrites materials increased with frequency and Zr4+-Co2+ content (x). Complex impedance spectroscopy formalism using the Cole-Cole plots indicated that most dielectric responses arise from grain boundary contributions. [ABSTRACT FROM AUTHOR]

Lanthanum (La3+) substituted Mg-Cd-Bi ferrite nanoparticles were synthesized by sol-gel auto combustion route consuming high quality nitrates. The impact of lanthanum concentration on microstructural and electrical properties in the ferrite series Mg 0.5 Cd 0.5 Fe 1.95 Bi 0.5-x La x O 4 (x = 0.0, 0.01, 0.02, 0.03, 0.04, 0.05) was investigated. The samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscope (SEM), and Current-voltage (I-V) analyzerfor compositional, structural, morphological and electrical analysis. Upon varying the lanthanum content, it is observed that all the samples retained perovskite BiFeO 3 phase with distorted rhombohederal structure. Furthermore, it is revealed that the sintering process can significantly control the structural defects and crystal imperfections which affect the electric and magnetic nature of ferrites. The conduction process in La3+-dopedferrite series is originated by the hopping of electrons between ions of same elementswhich reduced the electrical resistivity and depicts the semiconductor nature of synthesized samples.Thus, it is believed that the optimal doping of lanthanum content in La3+-substituted Mg-Cd-Bi ferrites followed by post-annealing can remarkably tune the electrical properties of synthesized ferrite nano particles. [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]

The yttrium substituted cadmium ferrites having composition Cd 1-x Y x Fe 2 O 4 (X = 0.00, 0.125, 0.250, 0.375, 0.500) were synthesized by the co-precipitation method and sintered at 1100 °C for 6 h. Structural, morphological, electrical, optical and dielectric characteristics were explored by XRD, SEM, EDS, FTIR, I–V two probes, UV–Vis and LCR techniques.XRD results confirmed the cubic structure of spinel ferrites. A decrease in lattice constants of the prepared samples was observed with the substitution of Y ions and was attributed to the difference in ionic radii of Y3+ (0.95 Å) and Cd2+ (0.97 Å) ions. Cationic distributions, ionic radii of both tetrahedral and octahedral sites, tolerance factor, oxygen positional parameters, bond lengths, interatomic distances, positional parameters and bond length angles were calculated from XRD data. The morphology of the prepared ferrites was studied using SEM and results ratified the XRD results. EDS confirmed the presence of all inserted elements in Cd 1-x Y x Fe 2 O 4 composition. DC resistivity and drift mobility of soft-ferrites were found to be increased from 1.047 × 108–4.822 × 1010 Ω-cm and 5.87 × 10−12 – 1.045 × 10−14 cm2V−1s−1, respectively, at 523 K with yttrium content confirming the behavior of semiconductor materials. The optical band gap energy calculated from the UV–Vis pattern of the Cd 1-x Y x Fe 2 O 4 system was decreased from 3.6011 to 2.8153 eV. DC resistivity and optical band gaps exposed inverse relation. FTIR results revealed lower and upper-frequency absorption bands in the ranges of 419.31–417.01 cm−1 and 540.95–565.70 cm−1, respectively. Dielectric constant and dielectric losses were in decreasing order, while ac conductivity revealed rising behavior with increasing frequency. Results showed the potential of yttrium doped Cd nanoferrites for applications in high-frequency microwave absorbing devices. [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]

Due to their low cost, easy preparation, and outstanding electrical, dielectric, and magnetic properties, spinel ferrites are of enormous scientific and technological importance. Moreover, graphene nanoplatelets (GNPs) are an excellent supporting material for the construction of a wide range of composites. The sol-gel auto combustion (SGAC) route was used to prepare Ni 0.5 Co 0.5 Fe 1.97 Nd 0.03 O 4 (NCNF) ferrite and their composites with GNPs. Single-phase structures were found by X-ray diffraction (XRD) analysis and the crystallite size increased with the insertion of GNPs into the NCNF sample. Raman spectra also confirmed the spinel structure of the ferrites and supported the existence of graphene in the composite. Micrographs indicate that agglomeration decreased in all the samples. It was found for the NCNF/2.5 wt%GNPs composite, the energy bandgap was 1.90 eV, while the temperature coefficient of resistance (TCR) had a value of −4.27 K−1 and the values of the dielectric constant and quality (Q) factor were a maximum. Moreover, the dielectric tangent loss was minimum, and magnetic tangent loss was maximum for the NCNF/2.5 wt%GNPs composite. A saturation magnetization of 108.83 emu/g and 24.06 GHz microwave frequency were observed for NCNF/2.5 wt%GNPs composite. Therefore, the composite NCNF/2.5 wt%GNPs had improved dielectric characteristics making them a promising material for a variety of applications, including microwave frequency operating devices, bolometric devices, and microwave absorbing materials. [Display omitted] • Sol-gel auto combustion was used to synthesize Ni 0.5 Co 0.5 Fe 1.97 Nd 0.03 O 4 /GNPs composites. • XRD and Raman analysis was used to study the structure. • The energy bandgap had a value of 1.90 eV for NCNF/2.5 wt%GNPs composite. • The peak position of temperature versus temperature coefficient of resistance (TCR) percentage plots occurs at 382 K. • The dielectric tangent loss was minimum, and magnetic tangent loss was maximum for NCNF/2.5 wt%GNPs composite. • The NCNF/2.5 wt%GNPs composite promising candidate for bolometric devices, microwave absorbing materials & frequency operating devices. [ABSTRACT FROM AUTHOR]

Present work reports the synthesis of RE3+ (La3+, and Ce3+) and Co2+ co-doped Zn 0.75 Cu 0.25 Fe 2 O 4 samples powder using sol-gel auto combustion process. Rietveld refinement established the spinel matrix with the space group (F d -3 m) and suggests that the uniform distribution of cations at the tetrahedral and octahedral lattice sites. The comparative study of crystallite size (D) was found using the Scherrer's relation, Scherrer's plot, Williamson-Hall (W–H), and Size-Strain (SS) plot methods for the as-prepared ferrites. The absorption band analysis confirmed the characteristic band absorptions lie in the frequency range of (577.82–418.84) 102 × m−1. Moreover, the electrical resistivity (ρ) measurements showed that the Co–Ce doped ZCF sample is highly resistive as compared to the other samples. The dielectric measurements revealed a dispersion pattern at lower frequencies and an almost frequency-independent pattern at higher frequencies. The field dependence of the dM/dH curve shows a magnetically well stable state and good crystallization cubic matrix of all the samples. The field dependence of the dM/dH curve at 303 K suggests that the increasing peaks separation and height for the as-prepared ferrites are owing to the existence of good magnetic stability and crystallization. [Display omitted] • Sol-gel auto-igniting process used to prepare RE3+ (La3+, and Ce3+) and Co2+ co-doped Zn 0.75 Cu 0.25 Fe 2 O 4 samples powder. • Rietveld refinement confirmed uniform distribution of cations. • The microwaves operating frequency (ω m) lies within the range of 5.31–10.91 GHz. • Well, crystallization and magnetic stability of all the as-prepared samples. [ABSTRACT FROM AUTHOR]

Lanthanum doped Z n 0.5 C o 0.5 L a x F e 2 − x O 4 spinel ferrites were synthesized through the co-precipitation technique. To characterize the structural, vibrational, electro-optical, dielectric, and thermoelectric properties, the following characterization techniques X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Raman spectroscopy, I–V measurement analysis, UV–vis spectroscopy, LCR meter, Seebeck analysis, and Energy dispersive X-ray analysis (EDX) were used. The XRD patterns showed nano-crystalline single-phase structure formation. Moreover, the lattice constant increased from 8.3909 ± 0.0042 Å to 8.3994 ± 0.0042 Å, and the crystallite size reduced from 33.6 to 17.5 nm with increasing La3+ cations. The bond angles showed stronger A – A and A – B interactions and weak B – B interactions with the addition of La3+. FTIR spectra showed the existence of the M − O stretching band and functional group study. The resistivity, optical band gap, and activation energy had maximum values at x = 0.1. At room temperature (RT), the dielectric parameters were recorded between the range of 8 Hz to 8 MHz. The Seebeck voltage coefficient was obtained for the as-prepared nano-ferrites to determine the charge carrier type. The EDX spectra showed a compositional distribution of the elements in all the samples. • Z n 0.5 C o 0.5 L a x F e 2 − x O 4 nano ferrite powder was prepared via the co-precipitation route. • Single-phase crystal structure and crystallite size decreased with La3+ in Zn–Co ferrites. • The optical band gap and DC resistivity were maximum at x = 0.1. • Z n 0.5 C o 0.5 L a 0.1 F e 1.9 O 4 has a small dielectric tangent loss at low frequency. [ABSTRACT FROM AUTHOR]

Lanthanum substituted Mg–Ni–Cu–Co ferrite nanoparticles prepared through the Sol-Gel method were studied using different methods such as XRD, FTIR, UV-VIS, SEM, Raman, LCR, EDX and IV to evaluate the structural, optical and electrical properties. The single-phase cubic spinel structure of the prepared samples was confirmed from X-ray diffraction analysis. The FT-IR spectra indicated two absorption bands, ν 1 and ν 2 that represent the complex Fe3+–O2− at A-site (tetrahedral) and B-site (octahedral) vibration. The optical band gap decreased from 2.48eV to 1.53eV observed by UV–Vis, and matched with the electrical resistivity measurements. Variation in the lattice parameters from XRD, the absorption band (octahedral) from FTIR, the optical energy band gap from the UV–vis data and the DC resistivity demonstrated change in structural, optical and electric properties of Mg–Ni–Cu–Co ferrites nanoparticles due to the addition of the rare earth element La3+. Both the dielectric losses and dielectric constant of the prepared samples decreased due to the La3+ ions doping, and A.C conductivity increased with increasing the value of frequency from 8 Hz to 8 M Hz. The variation in Raman peaks reveals that Raman shift varied due to the La3+ addition. EDX data confirmed the stoichiometric calculations of La3+ions substituted into Mg–Ni–Cu–Co ferrite nanoparticles. [ABSTRACT FROM AUTHOR]