Sol-gel Auto-combustion Route Research Articles

Exploring the synergistic effects of La3+ substitution on dielectric performance of manganese cobalt ferrite: Implications for advanced electronic applications

La3+ substituted Mn0.5Co0.5Fe2O4 ferrites were synthesized through sol-gel auto-combustion route. The impacts of varying doping concentrations (0.03, 0.06 and 0.09) were studied on synthesized samples' structural, optical, morphological, vibrational, and dielectric properties. The spinel cubic phase of synthesized samples was confirmed by X-ray diffraction (XRD) analysis; increased La3+ concentration has altered the structural parameters of prepared ferrites. Diffuse Reflectance Spectroscopy (DRS) shows a decrease in band gap with increasing concentration of La3+. Morphology has been reviewed by Field Effect Scanning Electron Microscope (FE-SEM), and elemental composition was confirmed by Energy Dispersive X-ray (EDAX) spectra. In addition, M − O stretching bonds were verified employing Fourier Transform Infrared (FTIR) spectroscopy. Raman Spectroscopy shows five modes, further confirming the spinel structure. The XPS spectra verified the +2 oxidation state of Manganese. Finally, the dielectric constant, tangent loss, and AC (Alternating Current) conductivity were analyzed with temperature at several frequencies. The experimental results have unveiled intriguing findings: the dielectric constant exhibited its maximum value at the lowest frequency within the investigated range, and it demonstrated an increasing trend with the rising temperature at a specific frequency. Notably, introducing La3+ through substitution has led to a noteworthy enhancement in the dielectric constant, underscoring the novel impact of this dopant on the material's electrical properties. A positive correlation existed between AC conductivity and temperature; as the temperature increases, so does the AC conductivity. Also, it was found to be maximum at maximum frequency value for all samples. Additionally, it can be deduced that raising the La3+ concentration in crystal improves the dielectric characteristics of Manganese Cobalt ferrites.

Efficient photocatalysis of Zn1-2xEuxDyxO nanoparticles towards the degradation of hazardous Rhodamine B dye

Industrial waste is the principal source of highly toxic organic and heavy metals. Treating such effluence is highly required to provide a clean ecosystem for living organisms. Photocatalysis is one of the most efficient, economical, and time-efficient ways for the removal of industrial wastes. In the current search, we propose to prepare a series of Zn1-2xEuxDyxO samples (x = 0.00–0.05), using the simple sol-gel auto-combustion route. The XRD results indicated a hexagonal structure for all samples. The presence of europium and dysprosium elements and their successful doping into the ZnO were proved by XRD and EDX analyses. The mean crystallite size and the values of band gap energy were altered by the Eu and Dy doping. The photocatalytic action of Zn1-2xEuxDyxO samples was assessed for Rhodamine B degradation. The experiments indicated a degradation with an efficiency of 99.1%, 95.1%, and 97.4% for Zn0.98Eu0.01Dy0.01O, Zn0.94Eu0.03Dy0.03O, and Zn0.90Eu0.051Dy0.05O samples, respectively within 90 min. The Zn0.98Eu0.01Dy0.01O sample exhibited the maximum photocatalytic efficiency with an excellent rate constant (r = 0.054 min−1) among all samples. The obtained findings demonstrated that the Eu and Dy co-doping at a specific concentration is a useful way to reach an effective photocatalytic activity of ZnO nanoparticles.

Mg1-xNixGayFe2-yO4 nano catalysts for green hydrogen generation with highly efficient photo/electro catalytic water splitting applications

The production of nanomaterials for renewable energy as fossil fuel substitutes is anticipated as a viable solution to the pressing issues of environmental pollution and energy scarcity. We fixated on the development of Mg1-xNixGayFe2-yO4 (x = y = 0.0–0.03; steps: 0.01) nanocatalysts by sol-gel auto-combustion route (SGAC) for the hydrogen generation through overall photo and electrocatalytic water splitting. The spinel cubic phase with Fd3m space geometry was established from XRD results. FESEM images shows cubic and spherical formed grains with definite grain boundaries and grain size of 164 and 184 nm for the MgFe2O4 and Mg0.98Ni0.02Ga0.02Fe1.98O4 nanomaterials. Soft magnetic behavior with superior saturation magnetization (Ms) and moderate coercivity (Hc) of 2.72–29.24 emu/g and 51.23–257.86 Oe was obtained for all of the developed nanocatalysts. According to the research findings, Mg0.98Ni0.02Ga0.02Fe1.98O4 nanocatalyst shows the highest photocatalytic activity of 11.38 mmol gcat−1. The as-synthesised photocatalysts' repeatability and stability were evaluated throughout repeated runs of a 4-h reaction period conducted under identical circumstances. On the other hand, the electrocatalytic studies were carried via 3-electrode arrangement (i.e., working, counter and reference) in 0.5 M H2SO4 and 0.1 M KOH electrolytes for hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). The overpotential for the MgFe2O4, Mg0.99Ni0.01Ga0.01Fe1.99O4, Mg0.98Ni0.02Ga0.02Fe1.98O4, and Mg0.97Ni0.03Ga0.03Fe1.97O4 electrocatalysts at 10 mA/cm2 were −0.866, −0.82, −1.02 and −0.92 V. Consequently, owing to these photocatalytic and electrocatalytic water splitting traits, the prepared nanocatalysts are highly efficient for hydrogen generation. However, MgFe2O4, and Mg0.99Ni0.01Ga0.01Fe1.99O4 nanomaterials show high zone of inhibition (ZOI) against Bacillus subtilis and Pseudomonas aeruginosa and therefore, making it valuable also for biological usages.

Photocatalytic and electrocatalytic hydrogen production promoted by Nd/La substituted cobalt–nickel magnetic nanomaterials

The current work concentrates on the design of Nd/La doped Co0.7Ni0.3Fe2O4 nanocatalysts for the green, clean, and sustainable generation of hydrogen through overall photocatalytic and electrocatalytic water splitting routes using sol-gel auto-combustion route. The spinel symmetry with a Fd3m geometry and cubic polycrystalline nature was observed for the developed catalysts. Spherical formed agglomerated nanoparticles having average grain size of 127.10 and 120.08 nm was confirmed for the produced Co0.7Ni0.3Fe2O4 and Co0.7Ni0.3Nd0.02La0.02Fe1.96O4 catalysts through the FESEM results. Maximum saturation magnetization (Ms) of 64.81 emu/g and coercivity (Hc) of 1234.54 Oe were attained by undoped Co0.7Ni0.3Fe2O4 catalyst. This shows the superior magnetic behaviour of our prepared catalysts, for magnetic recording applications. The estimation of photocatalytic hydrogen production for the prepared photo nanocatalysts was conducted under ambient conditions, with an irradiation from a UV-visible light having wavelength range of 200–2400 nm. The prepared Co0.7Ni0.3Nd0.03La0.03Fe1.94O4 photocatalyst shows the maximum photocatalytic activity of 12.57 mmol gcat−1. Also, the photocatalytic hydrogen evolution, repeatability, and stability of all the prepared catalysts were analyzed at three successive cycles. The third cycle showed a little drop in photocatalytic hydrogen evolution to 11.26 mmol gcat−1 as compared to the first cycle. On the other hand, the electrocatalytic activity of produced electrocatalysts were determined towards the electrocatalytic HER via a three-electrode system in 0.5 M H2SO4 electrolyte. The produced Co0.7Ni0.3Nd0.03La0.03Fe1.94O4 nanocatalyst shows excellent electrocatalytic HER activity as compared to other samples. Hence, with photocatalytic/electrocatalytic water splitting traits, the prepared nanocatalysts are highly efficient and suitable for the production of clean and green hydrogen energy sources.

Optical, magnetic, and electrochemical properties of a fluorite-perovskite Ce0.9Gd0.1O2-∂ - La0.6Sr0.4FeO3-∂ nanocomposite synthesized by one pot sol-gel auto-combustion route

Gadolinium-doped cerium oxide (Ce0.9Gd0.1O2-∂; CGO) and strontium-doped lanthanum ferrite (La0.6Sr0.4FeO3; LSF) are well-known compounds for their application in solid oxide fuel cells, dense oxygen permeable membrane, and high-temperature ceramic reactor. The superior electro-catalytic performance of these two individual oxides or their composites is well established as it originates from multivalent cations (Ce3+/4+ and Fe2+/3+/4+) and doping-induced defects like electrons, holes, and oxygen vacancies. This work focuses on synthesizing and characterizing composite taking CGO and LSF in different weight ratios, i.e., 10:90, 30:70, 50:50, 70:30, and 90:10 by sol-gel auto-combustion process. End members CGO and LSF were also synthesized for comparison purposes. All synthesized nanopowders (single phases and their composites) were characterized with X-ray diffraction (XRD) for phase identification and Scanning electron microscopy (SEM) for elemental composition analysis. XRD and SEM results established the formation of the required phase and targeted composition. The optical properties of the materials were evaluated with the help of ultraviolet–visible Diffuse Reflectance Spectroscopy (UV–Vis DRS). Tauc's approximation measured band gap energies, and all the composites showed a very high band gap in the 4.85–5 eV range. Magnetic properties such as saturation magnetization (Ms), remanence (Mr), and coercive force (Hc) were calculated from a magnetic hysteresis loop obtained from the Vibrating-sample magnetometer (VSM) experiment at room temperature. Furthermore, the law of approach to saturation (LAS) model was applied to more precisely calculate Ms and other essential parameters. In magnetic characterization, the LSF phase fraction controls the overall magnetic property of the composites. Electrochemical behavior, such as the composites' charge storage ability and stability were tested by cyclic voltammetry and chronopotentiometry method. All the samples exhibited good stability, and the highest specific capacitance of 26 F/gm was obtained for the composite sample (CL91) when only 10 % LSF phase was incorporated in the nanocomposite.

Investigation on bio-synthesized Ni- and Al-doped cobalt ferrite using lemon juice as eco-fuel

Pure and doped cobalt ferrite (CoFe2O4) nanoparticles were prepared using sol-gel auto-combustion route with the aid of lemon juice as eco-fuel. In this study, Ni2+ and Al3+ ions were chosen as the dopants. The cubic spinel crystal structure of the synthesized ferrite samples was elucidated from the powder X-ray diffraction analysis. The crystallographic parameters associated with the samples were obtained from the Rietveld profile refinement of the diffraction patterns. The precise lattice parameter obtained from the Nelson-Riley extrapolation method is found nearly matches with the lattice parameter obtained from the Rietveld refinement of respective samples. The average crystallite size and microstrain accompanying with the samples were estimated from various methods such as via the Debye-Scherrer method, Williamson-Hall analysis and size-strain plot. By employing Tauc’s plot method, the optical parameters such as the direct bandgap, sub-bandgap and the Urbach energy of all the samples were calculated by analyzing the UV-Visible reflectance spectra. The room temperature magnetic properties of all the samples were estimated from the vibrating sample magnetometry. The nature of magnetic hysteresis revealed the semi-hard ferrimagnetism of the prepared cobalt ferrite samples. Also, the variation of magnetic properties with doping was analyzed. The weakening of interaction among the ions in tetrahedral and octahedral sites causes a decrease in the values of remanent magnetization, saturation magnetization and coercivity of doped samples.

Structural, surface, magnetic, and dielectric properties of Ni0.3Cu0.3Zn0.4Fe1.4Cr0.6O4 spinel ferrite nanocrystals prepared by sol-gel auto combustion route

Structural, surface, magnetic, and dielectric properties of Ni0.3Cu0.3Zn0.4Fe1.4Cr0.6O4 spinel ferrite nanocrystals prepared by sol-gel auto combustion route

Impact of magnetic spinel ferrite content on the structure, morphology, optical, and magneto-dielectric properties of BaTiO3 materials

Abstract In this study, the influence of magnetic content of NiFe1.93Dy0.07O4 spinel ferrite on the structural, morphological, optical, and magneto-dielectric properties of BaTiO3 materials was investigated. NiFe1.93Dy0.07O4 magnetic nanoparticles and BaTiO3 dielectric materials were firstly synthesized using the hydrothermal method and sol–gel auto-combustion route, respectively. Then, different contents of the magnetic nanoparticles were added to BaTiO3 to form a series of BaTiO3/(NiFe1.93Dy0.07O4) x samples (abbreviated as BTO/(NDFO) x ) with x = 0, 2, 5, 10, 20, and 100 %. The analysis of the structure via X-ray diffraction (XRD) technique revealed a transformation from a tetragonal structure for the pristine BTO sample to a cubic structure upon the inclusion of magnetic nanoparticles. The morphological observations and chemical composition analyses via scanning electron microscope (SEM) coupled with EDX system showed the successful formulation of biphasic products. The optical properties were investigated, and it was found that the inclusion of the magnetic phase diminishes the bandgap energy (E g ) of final BTO/(NDFO) x samples. Furthermore, vibrating sample magnetometer (VSM) was used to investigate the magnetization properties. The values of saturation magnetization (M S ) and remanent (M r ) magnetization are rising with the increase of magnetic phase content. However, the coercivity (H c ) does not show a regular variation with the increase of NDFO content. The dielectric properties were also investigated for different BaTiO3/(NiFe1.93Dy0.07O4) x samples. The obtained results showed that the real permittivity (ε′) and dielectric tangent loss (tan δ) increased with increasing temperature. Remarkably, the addition of magnetic content provokes a reduction in tan δ values compared to the pristine BTO sample. The lowest values of tan δ and highest frequency stability were noticed in the sample added with 10 % of magnetic phase. The impedance and modulus were also determined and discussed.

Zircon-Type CaCrO4 Chromite Nanoparticles: Synthesis, Characterization, and Photocatalytic Application for Sunlight-Induced Degradation of Rhodamine B.

The degradation of organic dye pollutants is a critical environmental issue that has garnered significant attention in recent years. To address this problem, we investigated the potential of CaCrO4 chromite (CCO) as a photocatalyst for the degradation of cationic and anionic dye solutions under sunlight irradiation. CaCrO4 was synthesized via a sol-gel auto-combustion route and sintered at 900 °C. The Rietveld refined XRD profile confirmed the zircon-type structure of CaCrO4 crystallized in the tetragonal unit cell with I41/amd space group symmetry. The surface morphology of the sample was investigated by field emission scanning electron microscopy (FESEM), which revealed the polyhedral texture of the grains. Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) studies were carried out to analyze the elemental composition and chemical states of the ions present in the compound. Fourier transform infrared (FT-IR) spectroscopy analysis revealed the vibrational modes corresponding to the tetrahedral and dodecahedral metal oxide bonds. The optical band gap was approximated to be in the range of 1.928 eV by using the Tauc relation. The CaCrO4 catalyst with different contents (5, 20, 35, and 50 mg) was investigated for its photocatalytic performance for the degradation of RhB dye solution under sunlight irradiation using a UV-Vis spectrometer over the experimental wavelength range of 450-600 nm. The degradation efficacy increased from 70.630 to 93.550% for 5-35 mg and then decreased to 68.720% for 50 mg in 140 min under visible light illumination. The comparative study demonstrates that a higher degradation rate was achieved for cationic than anionic dyes in the order RhB > MB > MO. The highest deterioration (93.80%) was achieved for the RhB dye in 140 min. Equilibrium and kinetic studies showed that the adsorption process followed the Langmuir isotherm and pseudo-second-order models, respectively. The maximum adsorption capacity of 21.125 mg/g was observed for the catalyst concentration of 35 mg. From the cyclic test, it has been observed that the synthesized photocatalyst is structurally and morphologically stable and reusable. The radical trapping experiment demonstrated that superoxide and hydroxyl radicals were the primary species engaged in the photodegradation process. A possible mechanism for the degradation of RhB has been proposed. Hence, we conclude that CaCrO4 can be used as an efficient photocatalyst for the remediation of organic dye pollutants from the environment.

Influence of doping on magnetic and electromagnetic properties of spinel ferrites

In this study, spinel Ni0.5Zn0.5Fe2O4 doped with transition metal ions as well as rare-earth ions Ni0.4Zn0.4M′0.2Fe2O4 (M′ = Cu, Dy, Gd and Lu) and M″0.5Zn0.5Fe2O4 (M″ = Ni, Mn and Co) are developed using the sol-gel auto-combustion route, and the role of substitution on electromagnetic properties is investigated. The powder X-ray diffraction accompanied by Rietveld refinement signifies a single-phase spinel ferrite that belongs to Fd-3m space group for all the compositions. Rietveld refinement confirms that doped Cu2+, Dy3+, Gd3+ and Lu3+ ions are at random distribution between spinel tetrahedral and spinel octahedral sites against their preferential occupancy. The saturation magnetisation (MS) of Ni0.5Zn0.5Fe2O4 (MS = 50.5 emu/g) increased with partial doping showing MS = 60.08 emu/g for transition-metal doped Ni0.4Zn0.4Cu0.2Fe2O4 and MS = 109.7 emu/g for rare-earth doped Ni0.4Zn0.4Dy0.2Fe2O4, which was the highest among all the doped compositions. Doping enhances the dielectric permittivity of Ni0.5Zn0.5Fe2O4 from 4.2 to 6.5 for Ni0.4Zn0.4Cu0.2Fe2O4 and 7.7 for Ni0.4Zn0.4Dy0.2Fe2O4. Further, the reflection coefficient (RL) of all the doped compositions of Ni0.4Zn0.4M′0.2Fe2O4 (M′ = Cu, Dy, Gd and Lu) was less than −8 dB (85% absorption) throughout the frequency band of 8–12 GHz with an optimum material thickness of 3.5 mm. Transition metal ion doped Ni0.4Zn0.4Cu0.2Fe2O4 resulted in further improvement of its absorption characteristics of the incident EM waves with reflection coefficient (RL) less than −10 dB (between 84.15% and 90%) between 10 and 12 GHz at a material thickness of 3.5 mm in the X-band frequency range.

Structural, morphological, dielectric and ferroelectric properties of Nd substituted YFeO3 ceramics synthesized via sol gel auto-combustion route

The effect of Nd3+ ion substitution on the structural, morphological, ferroelectric, and dielectric properties of Y1-xNdxFeO3 (0 ≤ x ≤ 0.16) was investigated. The samples were prepared using the sol-gel auto-combustion route. The crystallite size was found to be in the range of 23 to 15 nm. The SEM exhibited that pure YFO shows an inhomogeneous shape of particles, while the substituted samples demonstrated a spherical shape and clusters of grains. The substitution of Nd3+ ions causes the splitting of vibrational characteristic bands υ1 from 450.71 to 479.1 cm−1 while characteristic band υ2 changes from 592.13.1 to 687.90 cm−1, respectively. The ferroelectric analysis indicated that polarization was 0.023 nC/cm2 to 0.007 nC/cm2 at a maximum applied field of 0.01 kV/cm. The dielectric constant of Nd3+ substituted YFO was increased as compared to pure YFO. All YFeO3 samples showed low values of tan loss (tanδ) es compared to pure YFO. Low dielectric losses of YFO suggest their utilization in multilayer chip inductors.

Impact of Co-doped NiFe2O4 (CoxNi1−xFe2O4) nanostructures prepared by co-precipitation route on the structural, morphological, surface, and magnetic properties

The excellent magnetic properties of spinel ferrite-based materials are preferably utilized in magnetic storage devices, and recording media. The magnetic properties of cobalt-doped nickel ferrite (Cox Ni1-xFe2O4) nanoparticles (NPs) were successfully investigated. A series of cobalt (Co)-doped nickel ferrite Cox Ni1-xFe2O4 NPs (x = 0.6, 0.7, 0.8, 0.9,1.0) were synthesized by the sol-gel method auto-combustion (SGAC) route. The crystallite sizes of the prepared CoxNi1−xFe2O4 NPs were found to be 23.5 ± 0.4, 25.3 ± 0.3, 25.0 ± 0.6, 29.5 ± 0.3, and 12.7 ± 0.3 nm for x = 0.6, 0.7, 0.8, 0.9, and 1.0, respectively, using X-ray diffraction (XRD) patterns. The random-shaped morphology with particle sizes was found to be 16.4 ± 0.8, 12.6 ± 0.1, 15.4 ± 0.7, 12.5 ± 0.2, and 11.9 ± 0.4 nm for CoxNi1−xFe2O4 (x = 0.6, 0.7, 0.8, 0.9, and 1.0), respectively, using high-resolution transmission electron microscopy (HRTEM). Tauc’s plot spectra of CoxNi1−xFe2O4 NPs showed that the direct band (2.01–2.42 eV) and indirect band gaps (0.86–1.16 eV) were tuned with Co2+ concentrations. The obtained binding energies (BEs) observed at (780–801 eV) for Co2+ and Co3+ions, (855–879 eV) for Ni2+ and Ni3+ ions, (710–760 eV) for Fe3+ and Fe2+ ions, and (529–531 eV) for O2- ions, respectively in CoxNi1−xFe2O4 NPs were confirmed by X-ray photoelectron spectroscopy (XPS). RT-dependent DC magnetization measurements exhibited saturation magnetization (45.28, 37.34, 33.32, 33.93, and 52.57 emu/g), coercivity (1090, 1160, 689, 507, and 377 Oe), retentivity (13.29, 12.86, 11.37, 8.10, and 10.18 emu/g), and magnetic anisotropy (4.834 ×106, 4.315 ×106, 4.037 ×106, 4.206 ×106, and 7.578 ×106 erg/cm3) for CoxNi1-xFe2O4 NPs (x = 0.6, 0.7, 0.8, 0.9, and 1.0), respectively. The improved magneto-crystalline anisotropy and decreased spin canting effect/ spin disorder for CoxNi1−xFe2O4 NPs indicated that the current research work can be suitable for magnetic storage devices and recording media.

Influence of Ni substitution on the magnetic properties of PrCoO3: A comprehensive study

The influence of nickel (Ni) ions on the structural and magnetic properties of PrCo1-xNixO3 perovskites was investigated. The samples were prepared using a sol-gel chemical auto-combustion route. The Rietveld refined X-ray diffraction patterns show that all samples were single-phase polycrystalline with orthorhombic (Pbnm) perovskite symmetry. Fourier transform infrared spectroscopy (FTIR) showed that with increasing Ni dopant content, the spin state changed from a low to an intermediate spin state (LS→IS), leading to an increase in the Co3+ population in the IS state, which improved the stability of the IS state. X-ray photoelectron spectroscopy confirmed the presence of mixed valence states (Co3+/Co4+) and oxygen vacancies. Ni-substituted PrCoO3 compounds exhibited mixed magnetic phases, which were separated by a theoretical model. The susceptibility curves were fitted with the Curie–Weiss law, and the negative value of the Curie–Weiss temperature indicated a strong predominance of antiferromagnetic (AFM) interactions over ferromagnetic (FM) ordering. However, when the Ni content in the host lattice increased, the FM coupling via double exchange became stronger. Thus, saturated FM ordering was achieved with an optimum doping level of Ni ions.

Synthesis, characterizations and magnetic properties of nanoscale CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) materials synthesized via sol-gel autocombustion route

Nanostructured materials of CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) have been synthesized by sol-gel autocombustion method. Phase purity and nanocrystalline nature of the materials were examined by powder XRD measurements. Morphology and microstructure of the materials were ascertained by FESEM technique. The estimated crystallite sizes (d) decrease from 30 nm to 8 nm, as a result of progressive increase in V content, x, in CoVxFe2-xO4 materials. The values of the observed lattice parameters (a) decrease continuously as a function of increasing V content, x, i.e. from 8.349(5) Å to 8.284(5) Å for the values of x = 0.0 and x = 0.9, respectively. Alterations of M − O bond lengths in CoVxFe2-xO4 materials in FTIR studies indicate the incorporation of vanadium in cobalt ferrite. The values of the saturation magnetizations (Ms) and coercivities (Hc) of CoVxFe2-xO4 materials are found to be in the range of 77.58 emu/g – 37.76 emu/g and 1264 Oe – 991 Oe for various values of x from x = 0.0 to x = 0.9, respectively. The observed trends in magnetic parameters of CoVxFe2-xO4 materials have been interpreted on basis of increasing vanadium content in the materials, cation distributions, size and surface effects.

Optimization of structural, dielectric, and magnetic properties of nanocrystalline copper doped spinel ferrites

Copper-substituted spinel ferrites with nominal composition Ca0.5Ba0.5-xCuxFe2O4 (x = 0.00, 0.125, 0.250, 0.350, 0.500) were successfully prepared by the sol–gel auto combustion route. The fabricated Nano-ferrites underwent a five-hour annealing process at 800 °C in a furnace. By the X-ray diffraction (XRD) analysis and dielectric measurements, the structural and electrical behavior of Ca0.5Ba0.5-xCuxFe2O4 nanoparticles were examined. Formations of a single-phase cubic structure of all prepared samples were estimated by the X-ray diffraction analysis. Crystallite size ranges from 37.43 to 50.07 nm. With the addition of Cu2+ cation, the lattice parameter, dielectric characteristics, and magnetic parameters were enhanced. It was observed that dielectric properties were improved significantly with the doping of copper. The dielectric constant and dielectric loss were found to decrease at high frequencies. On the other hand, an increase in AC conductivity was observed with increasing frequency by Maxwell Wagner and Koop's models. The VSM study confirms the improved magnetic properties of the sample. Remanent magnetization, saturation magnetization, and coercivity were improved significantly with the doping of copper cation. Based on these improved dielectric and magnetic characteristics, the prepared materials are strongly recommended for different electronic components and energy storage devices.

Impact of Holmium and Nickel Substitution on Y-Type Hexagonal Ferrites Synthesized via Sol-gel Method

Sol-gel auto combustion route is employed to fabricate Y-type hexagonal ferrites Ba2-xHoxSr2-yNiyFe12O22(x = 0, 0.02, 0.04, 0.06, 0.08, 0.1 & y = 0, 0.1, 0.2, 0.3, 0.4, 0.5). All prepared samples are examined through XRD, SEM, and dielectric characterization.The prepared samples were then sintered at 950 °C for 6 hours. TGA analysis was carried out to find the estimated sintering temperature for the phase development. The XRD experiment was performed to determine the effect of substitution on structural parameters. XRD crystallite size was observed in the range of 5.5 – 19.79 nm. Lattice constant (a) was found in the range 6.08 – 6.17 Å, and that of c was found in the range 44.08 – 44.73 Å. The averagegrain size value wasnoted to be around ~ 2?m as calculated through SEM.Through Raman spectroscopy, six active modes (3E1g, 2A1g, and E2g) correspond to different vibrational modes of the prepared samples. LCR technique showed that the dielectric constant and the dissipation factor were decreased with increased frequency. A decrease in dielectric losses suggests these materials are for high-frequency applications.

Effect of Sm3+ and Yb3+ doping on the structural and magnetic properties of La2−xRExNiMnO6 (x = 0.1–0.7) double perovskites

The doping effect of samarium (Sm) and ytterbium (Yb) at the La sites of La2NiMnO6 (LMNO) double perovskite on the structural and magnetic properties was studied. The rare-earth (RE = Sm, Yb) ion-doped La2-x RExNiMnO6 (x = 0.1–0.7) double perovskites were synthesized using sol-gel auto combustion route. The X-ray diffraction patterns of the Sm- and Yb-doped samples indicated single-phase monoclinic symmetry (P21/n space group). The Raman spectra provided complementary information of structural phase stability. The antisymmetric (∼528 cm−1) and symmetric (∼670 cm−1) stretching modes of vibration and a shoulder at wavenumber ∼250 cm−1 of the Raman spectra were consistent with a monoclinic phase. The X-ray photoelectron spectroscopy revealed the presence of La3+, Sm3+, Yb3+, Ni3+, Ni2+, Mn3+, and Mn4+ ions and improvement of the ordering of Ni2+ and Mn4+ ions in monoclinic structure of the Sm- and Yb-doped double perovskite structure. The temperature and magnetic field dependent magnetization studies revealed ferromagnetic nature with Curie temperature (TC) in the range of 205–265 K. The increase of Sm and Yb doping at the La sites of LMNO decreased TC and the presence of an additional weak magnetic transition at low-temperature range (∼100–150 K). The downturn feature of magnetization curves for a low-temperature regime (≤50 K) indicated a decrease of ferromagnetic exchange interactions and was a signature of spin freezing behavior in Sm- and Yb-doped LNMO samples.

Investigation on electrical transport and dielectric relaxation mechanism in TbCrO3 perovskite orthochromite

Herein, the TbCrO3 (TCO) chromite was synthesized by the sol-gel auto-combustion route and sintered at 900 °C. The Rietveld analysis of the room temperature powder X-ray diffraction profile confirmed the single-phase formation of the material crystallized in the orthorhombic phase of the perovskite structure with Pbnm space group symmetry. The surface morphology, the elemental composition, and the chemical states of the compound were investigated by field emission scanning electron microscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy, respectively. The electronic density of states, band structure, and electron density were analyzed by Density Functional Theory. The electrical transport and dielectric relaxation mechanism were investigated using complex impedance spectroscopy over the experimental frequency and temperature ranging from 40-1.2x106Hz and 138−273 K, respectively. Two semicircular arcs in the impedance complex plane plots were modeled to an equivalent circuit configured by RG∥QG+RGB∥QGB which were attributed to the contributions of the highly resistive grain boundaries and relatively conducting grains in the material. The electrical conductivity as a function of frequency followed Jonscher’s universal power law behavior and an increasing nature of the temperature-dependent frequency exponent suggested small polaron hopping as the electrical conduction mechanism of the material. The least capacitive response of the TCO system was investigated by the complex electrical modulus formalism and the frequency-dependent imaginary modulus spectra were modeled by the Kohlrausch–Williams–Watts function, which resolved the thermally activated peaks of bulk and interface effects to the dielectric relaxation mechanism. The dielectric constant exhibited Maxwell-Wagner interfacial polarization effects and the dielectric loss factor showed frequency dispersion at all temperatures.

Investigation of crystal structure, electrical and dielectric response of Ga3+ substituted Sr–Ni Y-type hexaferrites as a suitable material for high frequency applications

Technology important ferrites ceramic Sr2Ni2GaxFe12-xO22 (x = 0.00, 0.2, 0.4, 0.6, and 0.8) samples were produced using sol-gel auto combustion route. Structural, electrical, dielectric, and magnetic parameters were identified by substituting Ga3+ at the Fe3+ site. It was recognized that an increase of Ga3+ content in (Sr2Ni2GaxFe12-xO22) ceramic samples first decreased, then increased lattice parameters, and the density of samples was observed. This is because of the ionic radii and atomic weight of Ga3+ and Fe3+ cations. FTIR spectra show two characteristic absorption bands at 444-513 cm−1 caused by metal-oxygen vibrations. Due to the contribution of smaller grains of samples, the higher values of resistivity were observed, which vary from 3.78 × 1010 (Ω cm) to 1.13 × 1011 (Ω cm) by the substitution of Ga3+ ions at the octahedral site. The activation energy was measured between 0.20 and 0.61 eV. The dielectric response of Ga3+ substituted ferrite ceramic samples were studied in the 1 MHz-6 GHz frequency region. The Maxwell-Wagner bilayer model studied the effect of polarization with applied frequency on dielectric parameters. With the substitution of Ga3+, minimal losses in the range 0.34–0.44, about 6 GHz, and a high Q-value of about 10,000 were observed for each sample. In impedance spectroscopy analysis Cole-Cole plots confirm that the dielectric response is because of the influence of grain boundaries. The substitution of Ga3+ enhances saturation magnetization (68.20–71.78 emu/g) while coercivity decreases (655.86–507.86 Oe). In the present finding, the low dielectric loss, moderate permittivity, high value of the Quality factor, and very high value of resistivity of about 1.13 × 1011 that reduces the eddy current losses suggested that these materials are appropriate candidates for many high-frequency applications such as multilayer chip inductor, dielectric resonators, power applications, and microwave devices.

Synthesis of Mg-Ni-Zn ferrite Nanoparticles by Sol Gel auto combustion route and study of its structural and morphological characteristics

Synthesis of Mg-Ni-Zn ferrite Nanoparticles by Sol Gel auto combustion route and study of its structural and morphological characteristics