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The present work illustrates the synthesis and electrochemical performance of rGO-TiO2 composite electrodes for their potential application in energy storage devices. The rGO-TiO2 composite was prepared via ultrasonication method, and rGO-TiO2 electrodes were prepared by drop-cast technique. The rGO-TiO2 composite electrodes were electrochemically analyzed using galvanostatic charge–discharge (GCD) and cyclic voltammetry (CV) methods. These tests were performed with three distinct electrolytes (H2SO4, Na2SO4, and KOH), each with a 1 molar concentration. The rGO-TiO2 composite electrodes' specific capacitance (Csp) in 1 M H2SO4 electrolyte was estimated to be 4.89 F/g; it was estimated to be 3.35 F/g in case of 1 M Na2SO4 and 1.42 F/g for the 1 M KOH liquid electrolyte at a scan rate of 0.05 V/s. Using GCD, it was found that in the case of 1 M H2SO4, energy density and power density values were 1.78 Wh/kg and 4000 Wh/kg at a current density of 10 A/g, respectively; in 1 M Na2SO4, the energy density was found to be 2.58 Wh/kg, and conversely, in 1 M KOH, the energy density was measured as 2.39 Wh/kg at 1.25 A/g. AC impedance studies were conducted, and the prepared rGO-TiO2 electrodes exhibited specific capacitance values of 14.21 F/g, 12.68 F/g, and 15.02 F/g in H2SO4, Na2SO4, and KOH electrolytes, respectively. Hence, the research work demonstrated a simple and affordable method of synthesis of rGO-TiO2 electrodes that holds promise for supercapacitor applications, particularly when optimized for specific electrolyte conditions. [ABSTRACT FROM AUTHOR]

This study aims to enhance the multiferroic properties of bismuth ferrite (BFO) by investigating the effects of substitution with erbium (Er) on the material's structural, optical, and magnetic characteristics. Er-substituted bismuth ferrite (Bi1−xErxFeO3) (x = 0, 0.04, 0.08, 0.12, 0.16) nanoparticles (NPs) were synthesized via the very cost-effective Pechini modified sol–gel method followed by auto-combustion. X-ray diffraction (XRD) patterns confirmed the crystallinity, structure, and purity of the phase, revealing the formation of single-phase materials. The bond structure of the prepared samples was examined using Fourier transform infrared (FTIR) spectroscopy, confirming the significant stretching and bending of bonds of perovskites. Electron paramagnetic resonance (EPR) findings suggested a broadening of the signal as well as a shift of the center of resonance to lower fields. The experimental findings revealed that Er doping has a significant effect on the magnetic ordering and saturation magnetization of BiFeO3. In addition, UV–Vis spectroscopy demonstrated that the energy bandgap in the prepared samples varies from 2.13 eV to 1.71 eV. This research contributes to an understanding of the enhanced structural, magnetic, and optical properties of Er-substituted BFO nanoparticles, which is useful for designing and developing multiferroic materials with enhanced magnetic functionality for next-generation magnetoelectric devices, optoelectronic devices, and photocatalysts. [ABSTRACT FROM AUTHOR]

Magnesium-doped nickel ferrite nanoparticles with the chemical composition (Ni1−xMgxFe2O4, x = 0.00, 0.20, and 0.40) have been prepared by a modified sol–gel citrate method. Structural analysis was carried out through x-ray diffractograms (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The spherical-shaped morphology of the prepared nanoparticles has been confirmed by field-emission scanning electron microscopy (FESEM). The energy dispersive x-ray (EDX) analysis confirmed the presence of elements (Ni, Mg, Fe, and O) in the prepared compositions. The distribution of cations over tetrahedral and octahedral sites has been confirmed by Rietveld refinement using FullProf software. The phenomena of Maxwell–Wagner polarization is exhibited in the dielectric measurements. Cole–Cole plots showed that the net grain (Rg) and grain boundary resistance (Rgb) values are decreasing for the maximum concentration of Mg2+ ions in the nickel ferrites. Almost 96% deductions in the tangent loss values have been observed at high temperatures with the increasing concentration of Mg2+ ions in the nickel ferrites. Fitting of AC conductivity was carried out using the Jonscher Power Law function. The net magnetization saturation values also decreased from 27.7 emu/g to 16.7 emu/g upon the doping of Mg2+ ions in the pure nickel ferrites. These properties are all desired for materials working under high-frequency applications. [ABSTRACT FROM AUTHOR]

The research being conducted presents a glance into the effects of Gd substitution on the structural, magnetic, and dielectric properties of Bismuth ferrite by fabricating the series as Bi1−xGdxFeO3 (x = 0.0, 0.05, 0.10, 0.15, and 0.20) synthesized via Pechini’s modified sol–gel route. X-Ray Diffraction (XRD) data and Rietveld refinement of the XRD data revealed the phase purity and nanocrystalline nature of synthesized Nanoparticles (NPs). The substitution of Gd3+ ions lead to the structural distortion in BiFeO3 (BFO) NPs which is confirmed by the XRD Rietveld refinement. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirms the characteristic metal oxide bonds of FeO6 octahedra which accommodates the Gd3+ ions in BFO samples. The ferromagnetic ordering parameters decreased with increasing Gd3+ ions concentration in BFO NPs but observed the highest magnetization of 0.815 emu/g at x = 0.15 due to dominating ferromagnetic behavior, this phenomenon is well understood with Arrott’s plots. Electron Paramagnetic Resonance (EPR) spectroscopy was performed to investigate the electronic and magnetic interactions in the samples, the analysis revealed the presence of distinct resonance peaks associated with Gd3+ ions substitution, providing insights into the local magnetic properties, and the observed ferromagnetic behavior of the samples is also endorsed by the EPR analysis. The microstructural analysis was conducted by the use of Field Emission Scanning Electron Microscopy (FESEM) in conjunction with Energy-Dispersive X-ray Spectroscopy (EDS) which provided insights into the surface morphology and elemental composition of the examined samples. The FESEM and EDS elemental overlay images displayed well-defined grain boundaries and a homogeneous distribution of Gd3+ ions throughout the matrix. Dielectric spectroscopy was employed to investigate the dielectric properties of the synthesized NPs. The dielectric constant, loss tangent, and dielectric loss of the samples with Gd substitution were measured over multiple frequencies to observe the impact of Gd substitution on the dielectric properties. These findings contribute to the understanding of the multifunctional properties of perovskite materials and their possible applications in potential fields. [ABSTRACT FROM AUTHOR]

Substitution with rare earth (RE3+) and transition (X = Cu, Ni, Mn, Zn, etc.) metals can distort the spinel ferrite structure and create defects, which can be exploited in multifarious applications. In this study, yttrium and nickel co-substituted cobalt ferrites [Co1−xNixFe1.85Y0.15O4], (0.0 ≤ x ≤ 0.15) were synthesized by a modified sol–gel reaction route. The X-ray diffraction (XRD) patterns confirmed the single phase and highly crystalline nature of the prepared samples. Field emission scanning electron microscopy with energy dispersive X-ray (FESEM-EDX) spectroscopy confirmed the morphology of the prepared samples sintered at 800 °C and showed the grain sizes of the particles decreased with the addition of nickel ions. The simultaneous co-existence of saturation magnetization and ferroelectricity at room temperature confirmed the multiferroic nature of the co-substituted cobalt ferrites. The dielectric and impedance studies confirmed the Maxwell–Wagner polarization phenomenon and the enhanced values with Y–Ni co-substitution. The maximum saturation ferroelectric polarization was attained around 6.142 μC cm−2 for yttrium-substituted cobalt ferrite and then decreased with the increase in the substitution % of nickel. The maximum value of saturation magnetization (Ms = 99.50 emu g−1) was obtained with the highest substitution % of nickel of x = 0.15 in yttrium-substituted cobalt ferrite (YCFO) nanoferrites, which was also confirmed from the vibrating sample magnitude (VSM) studies at room temperature. The improvements in the structural, morphological, electrical, and multiferroic properties in the co-substituted cobalt ferrites were found to correlated to the substitution of the bigger cationic Y3+ ions compared to the Fe3+ ions, while the small substitution of Ni2+ ions lead to changes in the lattice parameters, porosity, and conduction behavior. These significant enhancements in co-substituted cobalt ferrites can be exploited for hydroelectric cell applications. [ABSTRACT FROM AUTHOR]

The inherently reduced electrical conductivity of transition metal oxides as electrodes in supercapacitors is of major concern to attain enhanced electrochemical performance. In this connection, efforts have been made to synthesize the perovskite oxide LaMnO3 by doping of Sr at the La site, i.e., La1−xSrxMnO3 (LSM) via the conventional sol–gel method. Powder x-ray diffraction pattern confirms the absolute phase formation of LSM nanoparticles with hexagonal structure. The micro-structural properties observed via scanning electron microscopy (SEM) show large specific surface area for charge storage. Among all samples, the La0.85Sr0.15MnO3 (LSM15) sample shows a higher value of current (0.054 A at 2 V and 0.145 A at 3 V) and higher conductivity. The cyclic voltammetry (CV) results displayed pseudo-capacitive behavior. The highest obtained specific capacitance for the symmetric LSM15 electrode is 40.5 F g−1 at a scanning rate of 20 mV s−1 in 0.5 M H2SO4. With the increase in scan rate, there is a decreasing trend seen in specific capacitance which shows low electrochemical performance at higher scan rates. The electrochemical impedance spectroscopy measurements confirmed that LSM is a dynamic supercapacitor candidate due to subsequent decrease in resistance with Sr doping in LaMnO3 which shows enhanced conductivity. [ABSTRACT FROM AUTHOR]