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Barium strontium titanate (BST), with varying Sr doping levels (x = 0, 0.05, 0.075, 0.1, 0.15, 0.3), was successfully synthesized using the solid-state reaction technique. The aim was to investigate the microstructural, dielectric, and impedance properties as Sr doping increases. X-ray diffraction analysis revealed a tetragonal phase structure for these materials, belonging to the P4mm space group, confirmed via Rietveld refinement using the Fullprof suite. SEM analysis indicated the decrement in grain sizes ranging from 0.198 to 0.0582 μm as doping concentration increases. The temperature and frequency dependencies of the dielectric constant were examined, with the Curie temperature observed in the range of 295 to 351 K with decreasing trend with substitution of strontium in pure barium titanate, showing an increase in dielectric constant with rising temperatures and non-relaxor behavior. P–E loops of BST samples illustrated bulk ferroelectric behavior, with maximum values of retentivity and coercivity reaching 1.56 and 13.97, respectively, in the highly doped BST sample. Various analytical techniques, including Nyquist plots, real and imaginary components of impedance, conductivity measurements, modulus formalism, and determination of charge carrier activation energy, were employed to elucidate the relationships between microstructure and electrical properties. Temperature-dependent resistivity demonstrated the negative temperature coefficient of resistance (NTCR) behavior in Sr-doped barium titanate. Impedance studies revealed semicircular arcs in Nyquist plots, indicating contributions from both grains and grain boundaries. The formation of well-defined grains in the BST samples was further confirmed through modulus spectroscopy. [ABSTRACT FROM AUTHOR]

Colossal magnetoresistance materials have demonstrated large changes in resistance in the presence of magnetic fields. In the current work, a group of such materials, with the compositional formula La0.67Ba0.33MnO3 and 10% Fe, Co, Ni, Zn doped La0.67Ba0.33MnO3 have been prepared by conventional solid-state method. Structural analysis has been carried out by X-Ray diffraction method followed by Rietveld analysis. Magnetic transition between ferromagnetism to paramagnetism has been observed from the magnetic characterizations. Parameters such as Curie temperature (θP) and effective magnetic moment (µeff) are obtained from susceptibility analysis subject to Curie–Weiss law. Furthermore, magnetocaloric nature of the samples is examined from the M-H isotherms. Using Maxwell's relations, isothermal entropy change, ∆Smax are determined to check whether the prepared samples can be used for magnetic refrigeration around the room temperature. [ABSTRACT FROM AUTHOR]

Almost 20 million tons of solvents are released in the nature per year. Solvents represent about 80% of the total volume of chemicals employed in chemical synthesis. Solvents are often flammable or toxic, calling for the replacement of conventional solvents by sustainable solvents. Recent sustainable solvents can be recovered and reused easily, and can efficiently support catalysts. Here we review key synthetic procedure using supercritical liquid CO2, polyethylene glycol, glycerol, ionic liquids and deep eutectic solvents. [ABSTRACT FROM AUTHOR]

Samarium-doped cobalt ferrite nanoparticles CoSmxFe2-xO4 (0 ≤ x ≤ 0.1) were synthesized using citrate gel auto-combustion method, followed by annealing at 500 °C for 4 h in air. The physical properties of the samples were evaluated using x-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, Mössbauer, magnetic, and dielectric measurement techniques. Rietveld analysis of XRD data confirmed the formation of a single-phase cubic spinel structure for all compositions. Experimental results indicated that doping with samarium (Sm) strongly affected the magnetic properties of CoSmxFe2-xO4 nanoparticles. The values of saturation magnetization (MS) were reduced from 62.99 (x = 0) to 41.17 (x = 0.1) emu/g. Room-temperature Mössbauer spectra show two sextets (tetrahedral and octahedral sites), and the values of the hyperfine magnetic field (Hhf) of both sextets are found to decrease with Sm-doping. The values of the isomer shift show that all Fe-ions are found in the Fe3+ state. The interstitial Sm ions positioned within CoFe2O4 realized a dielectric constant dispersion that displayed a maximum at low frequency. With an increase in samarium ion concentration, the two dielectric relaxations reached a very wide range of frequencies. This can be attributed to the contribution of conduction in the grains and grain boundaries of ferrite. Samples with samarium contents of 0.01 and 0.03 showed high impedance stability at 50 and 150 °C, respectively, rendering them suitable for use as a high-frequency window below 1 kHz. [ABSTRACT FROM AUTHOR]

Here in the present investigation, constituent phases of (1 − x)Mn0.7Zn0.3Fe2O4(MZFO) + (x)BaTiO3(BTO) (where x = 0.0, 0.25, 0.50, 0.75 and 1.0) composites have been synthesized by sol–gel auto-ignition route and the composite structure by ceramic route. The XRD analysis ensures that the composite structure consists of both cubic spinel piezomagnetic and perovskite piezoelectric phases. The average crystallite size estimated from Scherrer equation increases from 15.36 to 21.94 nm. The strain induced in individual phases has been investigated by W–H analysis and it is observed that the MZFO phase shows comprehensive type strain while BTO phase shows tensile type strain. Scanning electron micrographs confirm the microstructure of the sample with grain size ranges from 36.006 to 54 nm. Energy dispersive X-ray spectra and elemental color mappings of typical samples (x = 0.0 and 0.75) clearly indicates the phase purity and stoichiometric proportion of the composites. Fourier transform infrared spectra showed five major absorption bands related to stretching vibrations of different kinds of metal ions and oxygen ions. Increasing percentage of BTO phase in the composite reduces the saturation magnetization, remnant magnetization and coercivity. Real and imaginary parts of permittivity show maximum values at lower frequency region and decrease with increase in applied frequency. For the composition (0.25)MZFO–(0.75)BTO, composite shows maximum value of magnetoelectric coupling coefficient (αME = 20.45 mVcm−1 Oe−1). The improved magnetoelectric properties make MZFO–BTO composite applicable for electronic devices. [ABSTRACT FROM AUTHOR]

One-pot condensation of pyrazole-4-aldehydes and hydroxylamine hydrochloride to form the corresponding oxime using formic acid as a medium and further dehydration of oxime using a catalytic amount of orthophosphoric acid to afford novel pyrazole-4-carbonitrile. This protocol serves as an ortho-phosphoric acid-catalyzed one-pot conversion of aldehyde to nitrile. Most remarkable features of this method are metal-free, cost-effective, atom efficiency with excellent yield (98–99%). This process will serve as a robust and scalable tool for the synthesis of valuable and versatile precursor (nitriles). This precursor will pave the way for the synthesis of various medicinally important valuable compounds. [ABSTRACT FROM AUTHOR]

We have fabricated a high quality magnetic Ni0.5Zn0.5Fe2O4 ferrite powder/polymer composite sheet consisting of common and environmentally friendly elements only. The sheet was then tested for its dynamic permeability by irradiating with electromagnetic waves with frequencies up to 50 GHz. Two different originally developed methods were used for the high-frequency permeability measurements, a short-circuited microstrip line method and a microstrip line-probe method. It is challenging to measure the dynamic permeability of magnetic thin films/sheets beyond 10 GHz because of the low response signal from these materials. However, the two methods produced essentially equivalent results. In the frequency dependent permeability profile, the maximum position of the profile, μ max ″ , shifted towards higher frequencies upon increasing an applied (strong) static external magnetic field, H dc . A linear relationship between μ max ″ and H dc for the entire range of H dc was observed even at small H dc . In general, the spinel-structured Ni-based ferrites exhibit low magnetic anisotropy, but the present sample showed a uniaxial-anisotropic behavior in the parallel direction of the sheet. Our Ni0.5Zn0.5Fe2O4 powder/polymer composite sheet thus exhibits high performance at GHz frequencies, and should be applicable e.g. as an anisotropic electromagnetic wave-interference material. [ABSTRACT FROM AUTHOR]

Rare earth Ho3+-substituted Co–Ni ferrites having a chemical formula Co0.6Ni0.4Fe2−xHoxO4 (0.0, 0.025, 0.05, 0.075, and 0.1) were prepared via sol-gel route. The phase formation of these samples was confirmed by the thermogravimetric analysis with differential thermal analysis and X-ray powder diffraction techniques. Rietveld refinement confirms the cubic spinel structure of the prepared samples having space group Fd3− m with presence of secondary phase of α-Fe2O3. The lattice parameter is increased from 8.412 to 8.582 Å with Ho3+ ion concentration in cobalt–nickel ferrite from x = 0 to x = 0.1. The distribution of cations has been studied with the help of X-ray diffraction data and it is found that Ho3+ ions preferred to occupy the octahedral [B] site. The other structural parameters like X-ray density, bulk density, hopping length, and allied parameter are increased with the composition of Ho3+ ions in the Co–Ni ferrite. The morphology of the samples was observed by transmission electron microscopy and scanning electron microscopy showed the nanostructured formation. [ABSTRACT FROM AUTHOR]

This study explored the microstructural and magnetic features of NiFe2−xDyxO4 (x ≤ 0.10) NPs (nanoparticles) that were synthesized by sol–gel auto-combustion method. The single phase of spinel ferrite has been verified for all samples without any impurity. The cubic morphology of the products was also showed by SEM. Room temperature (300 K) and 10 K magnetization curves were recorded applying a dc magnetic field up to ±50 kOe and it was observed that magnetic features of NiFe2O4 NPs significantly changed by the substitution of Dy3+ ion. Magnetization measurements showed low order of 300 and 10 K magnetic parameters (such as Keff, coercivity and anisotropy field values), revealing soft ferrimagnetic behaviors of all pristine and doped NiDyxFe2−xO4 (0.00 ≤ x ≤ 0.10) NPs at both 300 and 10 K. Pristine NiFe2O4 has maximum magnetic moment and saturation magnetization values among all samples. Dy3+ substitution showed a slight decrement in magnetization values compared with pristine sample. A slight increase in coercivity was noticed with Dy3+ substitution. Squareness ratios (SQRs) have a range between 0.144 and 0.324. These values are smaller than the theoretical limit of 0.50, implying the multi-domain nature for NPs. Blocking temperature (TB) was calculated as 28 K for NiFe2O4 NPs. Highlights: NiFe2−xDyxO4 (x ≤ 0.10) NPs were prepared via sol–gel auto-combustion method. XRD analysis indicates the formation of pure single phase of spinel ferrites. NiFe2−xDyxO4 (x ≤ 0.10) NPs exhibit soft ferrimagnetic nature. All prepared NiFe2−xDyxO4 (x ≤ 0.10) NPs displayed a multi-domain nature. Blocking temperature (TB) was calculated as 28 K for NiFe2O4 NPs. [ABSTRACT FROM AUTHOR]

In this work, Y3−xBixAl0.5Fe4.5O12 nanoparticles in powder form with composition x = 0.0, 0.5, 1.0,1.5 and 2.0 were fabricated by a sol–gel auto-combustion technique and calcined at 1150 °C for 10 h. The analysis of X-ray diffraction patterns using Rietveld refinement suggests that Bi-substituted yttrium aluminum iron garnet (YAIG) samples crystallize in cubic structure with Ia- 3 ¯ d space group. The average size of crystallite of the samples calculated by the Scherer formula is found in the range of 19–24 nm which are in consistent with that of measured from Williamson–Hall curve. The absorption bands in Infrared spectra corresponding to garnet are shift to lower frequency with the increase of the Bi3+ concentration. Raman spectroscopy shows the non-vibrational behavior of Bi-substituted YAIG due to the excitation of Y3+ ions from the ground energy level. The morphology of the samples is observed by transmission electron microscopy and field emission scanning electron microscopy which showed most of the particles and grains are in spherical shape. The energy dispersive X-ray (EDS) spectra confirmed the elemental compositions of the selected sample. In UV–Visible spectroscopy, transparency of the samples decreases with increasing in Bi3+ ions substitution in YAIG. The saturation magnetization (Ms) decrease from the 14.59 to 2.25 emu/g with the increase in Bi3+ ions concentration, whereas, the values of coercivity (Hc) and retentivity (Mr) are very low. DC resistivity as a function of temperature shows the semiconducting nature of the synthesized samples and its decreased from 6.17 × 106 to 0.06 × 106 Ω-cm with the addition of Bi3+ ions. [ABSTRACT FROM AUTHOR]

We report a comprehensive evaluation of the microstructures, magnetic, and hyperfine traits of Ca2+/Mg2+ co-substituted strontium nanohexaferrites (SHFs) of chemical compositions Sr1–2xCaxMgxFe12O19 (x ≤ 0.1). These SHFs were prepared using sol–gel unified auto-combustion strategy and characterized by diverse analytical measurements to determine the effects of Ca2+/Mg2+ co-substitution on the aforesaid properties. XRD and high resolution transmission electron microscpe (HRTEM) analyses confirmed the nucleation of HF nanocrystallites. UV-visible diffuse reflectance (DR–UV–Vis) spectra were used to evaluate the optical band gap of the proposed SHFs, which was reduced with the increase in co-substitution contents. The 57Fe Mössbauer spectra was exploited to assess the quadrupole splitting, spectral line-width variation, isomer shift, distribution of cations (Ca2+ and Mg2+), and hyperfine magnetic fields. Measured magnetic parameters such as saturation magnetization, remanence, squareness ratio (SQR), coercivity, and magnetic moment were significantly improved due to the Ca2+/Mg2+ co-substitution. All the prepared SHFs revealed ferrimagnetic nature both at 10 and 300 K. Achieved SQR values ≈0.5 of the studied SHFs clearly disclosed their single domain character possessing uniaxial anisotropy. Highlights: Sr1–2xCaxMgxFe12O19 (x ≤ 0.1) SHFs via sol–gel auto-combustion method. Sr1–2xCaxMgxFe12O19 (x ≤ 0.1) SHFs exhibit hexagonal platelet-like structure. Mössbauer results of these SHFs showed a continuous decay in the hyperfine magnetic field up to x = 0.08 before being escalated beyond this concentration. Sr1–2xCaxMgxFe12O19 (x ≤ 0.1) SHFs exhibit ferrimagnetic nature both at 10 and 300 K. [ABSTRACT FROM AUTHOR]

Optical and thermodynamic behavior of three different phases of multiferroic BiFeO3 compound were investigated using first-principles calculations under the local (spin)-density approximation (L(S)DA) and TB-mBJ semi-local (Tran-Blaha modified Becke-Johnson) potential approximation methods by applying WIEN2k code. In order to study the ground state properties of this compound, the total energies were calculated as a function of reduced volumes using Brich Murnaghan equation. To explore the ferroelectric behavior, the real and imaginary parts of the dielectric functions were obtained at ambient conditions and analyzed using both the LSDA+ U and TB-mBJ potentials. In addition, thermodynamic properties were also obtained using Gibbs2 code. Finally, it has been concluded that the results obtained in the present investigations may be useful in predicting the properties of Bismuth ferrites for possible applications. [ABSTRACT FROM AUTHOR]

In the present investigation we have studied the role of varying pH and sintering temperature on the properties of copper ferrite nanoparticles synthesized from metal nitrate solutions by sol-gel auto-combustion technique. The CuFe2O4 samples were synthesized with varying pH values (without maintaining pH, pH 4 and 8). The careful analysis of X-ray diffraction (XRD) result showed that the pH provides boost to develop copper ferrite nanoparticles. The samples without maintaining pH suggested the presence of three different phases. The samples with pH values 4 and 8 showed the tetragonal structure. Crystal structure phase transformation of copper ferrite (pH 8) nanoparticles was studied under different sintering conditions. The prepared samples were characterized by XRD, field emission scanning electron microscopy, FTIR and magnetization. These copper ferrite nanoparticles sintered at different temperatures show combinations of cubic and tetragonal phases. The thermal behavior of as-prepared samples was confirmed by thermo gravimetric/differential thermal analyzer analysis. The morphology of materials was understood by SEM technique. The room temperature magnetic measurement proves strong redistribution of Cu2+ ions. Sintering temperature alerts the saturation magnetization (Ms) to a large extent from 9.26 to 25.15 emu/g. [ABSTRACT FROM AUTHOR]

Lanthanum-doped nano spinel ferrite compounds were synthesized via normal micelles method, characterized by means of TGA/DSC curves to know calcination temperature and stoichiometry of elements confirmed by EDAX. X-ray diffraction shows well defined cubic spinel structure with secondary phase of ortho ferrite LaFeO3. Lattice parameter exhibited gradual increases with increasing in La3+ ion concentrations due to the larger ionic radii of La3+ ions replace Fe3+ ions. FT-IR spectra recorded in the range of 4000-400 cm−1 to detect vibrational bands. Surface morphology analyzed by SEM, The particle size analyzed by Dynamic Light Scattering, full width half maxima of 311 peak obtained from XRD and TEM analysis, reveals that fine particle nature with little agglomeration and average particle size determined in the range of few nano meters. [ABSTRACT FROM AUTHOR]

The effect of synthesis techniques on the structural, magnetic and magneto-transport properties of LaNaMnO ( x = 0.1 and 0.2) manganites has been investigated. The samples were prepared using two different techniques: sol-gel and poly vinyl alcohol (PVA) precursor methods. X-ray diffraction studies indicate a rhombohedrally distorted perovskite structure having R3-c space group. The particle sizes of all the samples are in the nanometer range. A ferromagnetic insulating (FMI) behavior has been observed for x = 0.10 manganite synthesized using sol-gel technique while poly vinyl alcohol precursor method shows ferromagnetic metallic (FMM) behavior. A large magnetoresistance has been observed at low temperature region for x = 0.10 sample prepared using sol-gel method. The room temperature magnetoresistance values of sol-gel-prepared samples are found to be higher than that compared to PVA precursor method. Finally, theoretical work on magnetocaloric properties of the samples at ferro to paramagnetic state is presented and the results are explained qualitatively. [ABSTRACT FROM AUTHOR]

Manganites with the compositional formula, Nd A MnO (where A = Ca, Sr, Pb, and Ba) were prepared by the sol-gel technique. After characterizing the samples structurally, a systematic investigation of magnetization over a temperature range 10-300 K at 0.05 T magnetic field has been undertaken An effort has been made to calculate the magnetocaloric behavior of all the samples theoretically using the experimental magnetization data. The observed behavior has been explained qualitatively. [ABSTRACT FROM AUTHOR]

An effort has been made to calculate the magnetocaloric behavior of Sr-doped EuMnO by theoretically using the experimental magnetization data (at different magnetic fields) available in the literature. Other important parameters such as maximum entropy change, full width at half maximum, relative cooling power, and maximum adiabatic temperature change in 1 and 2 T magnetic fields were also computed. The observed behavior exhibited by the samples has been explained qualitatively. [ABSTRACT FROM AUTHOR]

Colossal magnetoresistive (CMR) materials with the compositional formula, NdAMnO (where A = Ca, Sr, Ba, and Pb) in the nanocrystalline form were prepared by the PVA gel technique. After characterizing the samples structurally, a systematic investigation of magnetization has been undertaken, over a temperature range 10-300 K at 0.05 T magnetic field. An effort has been made to calculate the magnetocaloric behavior of all the samples theoretically using the experimental magnetization data. Other important parameters such as maximum entropy change, full width at half-maximum, relative cooling power, and maximum adiabatic temperature change under 0.05 T were also computed. The observed behavior has been explained qualitatively. [ABSTRACT FROM AUTHOR]

CuCoZnFeO (0 ≤ x ≤ 0.5) nanoparticles are prepared by sol-gel auto combustion method, using copper nitrate, zinc nitrate, ferric nitrate, cobalt nitrate, and citric acid as the starting materials. The process takes only a few minutes to obtain as-received Co-substituted Cu-Zn ferrite powders. X-ray diffraction (XRD), vibrational sample magnetometer and thermo gravimetric analysis are utilized in order to study the effect of variation in the Co substitution and its impact on particle size, lattice constant, density, cation distribution and magnetic properties like magnetization, coercivity, remanent magnetization, ferritization temperature and associated water content. Lattice parameter found to increase with increasing Co content, whereas X-ray density, bulk density, particle size showed decreasing trend with the Co content. Cation distribution indicates that the Co and Cu ion show preference towards octahedral [B] site, Zn occupy tetrahedral (A) site whereas Fe occupy both tetrahedral (A) and octahedral [B] site. Redistribution of cations takes place for x > 0.3. Saturation magnetization (Ms) increases from 52.99 to 79.62 emu/g ( x ≤ 0.3), for x > 0.3 Ms decreases with increase in Co content x. However, coercivity, magnetocrystalline anisotropy and remanent magnetization increases with the Co substitution. [ABSTRACT FROM AUTHOR]

Ultrafine crystals of chromium-substituted nickel ferrite were prepared by wet chemical co-precipitation method using sulphates of respective metal ions. Formation of these materials has been confirmed by X-ray powder diffraction method. The fine crystal nature of these materials is evidenced from scanning electron microscope (SEM). Cation distribution has been investigated using X-ray diffraction technique. Cation distribution indicates that chromium occupy octahedral site for all the values of composition x. The saturation magnetization and magneton number both are decreasing with increase of chromium concentration x. The decrease in saturation magnetization and magneton number is attributed to the substitution of the Cr3+ ions. Curie temperature ( T C) from susceptibility plot is found to decrease with Cr concentration x. Curie temperature of all the compositions are also obtained theoretically and it agrees with observed Curie temperature. [ABSTRACT FROM AUTHOR]

Colossal magnetoresistance materials have demonstrated large changes in resistance in the presence of magnetic fields. In the current work, a group of such materials, with the compositional formula La0.67Ba0.33MnO3 and 10% Fe, Co, Ni, Zn doped La0.67Ba0.33MnO3 have been prepared by conventional solid-state method. Structural analysis has been carried out by X-Ray diffraction method followed by Rietveld analysis. Magnetic transition between ferromagnetism to paramagnetism has been observed from the magnetic characterizations. Parameters such as Curie temperature (θP) and effective magnetic moment (µeff) are obtained from susceptibility analysis subject to Curie–Weiss law. Furthermore, magnetocaloric nature of the samples is examined from the M-H isotherms. Using Maxwell's relations, isothermal entropy change, ∆Smax are determined to check whether the prepared samples can be used for magnetic refrigeration around the room temperature. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]