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Researchers are taking great interest in the synthesis and characterization of MnZn ferrites due to their wide range of applications in many areas. MnZn ferrites are a class of soft magnetic materials that have very good electrical, magnetic and optical properties. The properties of MnZn ferrites include high value of resistivity, permeability, permittivity, saturation magnetization, low power losses and coercivity. The above mentioned advantageous features of MnZn ferrites make them suitable for the use in various applications. In biomedical field these ferrites are used for cancer treatment and MRI. MnZn ferrites are also used in electronic applications for making transformers, transducers and inductors. These ferrites are also used in magnetic fluids, sensors and biosensors. MnZn ferrite is highly useful material for several electrical and electronic applications. It finds applications in almost every household appliances like mobile charger, LED bulb, TV, refrigerator, juicer mixer, washing machine, iron, microwave oven, mobile, laptop, desktop, printer and so on. Therefore, the present review focuses on different techniques for synthesis of MnZn ferrites in literature, their characterization tools, effect of doping on the properties of MnZn ferrite and finally we will discuss about their applications. [ABSTRACT FROM AUTHOR]

In the present work, the structural and magnetic properties of lithium-zinc ferrite ceramics of Li 0.4 Fe 2.4 Zn 0.2 O 4 composition, obtained using a complex high-energy impact including the mechanical activation of Fe 2 O 3 -Li 2 CO 3 -ZnO reagent mixture in planetary mill and radiation-thermal (RT) heating by continuous electron beam, were studied. The samples were divided into two batches: 1) with preliminary thermal synthesis; 2) without preliminary synthesis. All samples were studied by X-ray diffraction (XRD), electron microscopy (SEM) and thermal analysis (TG/DTG) techniques. It was established that the high density and low porosity of lithium-zinc ferrite ceramics can be received by using radiation-thermal heating. The samples are characterized by high values of specific magnetization and Curie temperature. Preliminary mechanical activation of the initial reagent mixture allows not only to accelerate the synthesis of ferrite materials, but also to combine the technological stages of synthesis and sintering in single stage of radiation-thermal processing. [ABSTRACT FROM AUTHOR]

The paper considers kinetic laws of lithium ferrite synthesis under heating of mixtures of the initial Fe 2 O 3 –Li 2 CO 3 reagents of different prehistory (powder, compact, mechanically activated mixture) with a high-energy electron beam. The synthesis temperature range was (600–750) °C, and the holding time was up to 120 min. The study employed an ILU-6 pulsed accelerator with electron energy of 2.4 MeV. Formation of ferrite in conventional thermal annealing at similar temperature and time conditions was studied for comparison. XRD analysis was the main method to study the synthesized samples. It is found that the rate of ferrite formation depends on both the heating method and the density and activity of the initial mixture. It is shown that high-energy electron beam heating of the mechanically activated mixture significantly accelerates ferrite production, which is indicated by decreased kinetic parameters of ferrite synthesis. [ABSTRACT FROM AUTHOR]

Mn–Zn ferrite magnetic nanoparticles (MNPs) were deposited by silica shell for magnetic separation purpose. Following the formation of MZF(core)@SiO 2 (shell), MZF@SiO 2 /BiOBr 0.5 Cl 0.5 nanocomposites were synthesized by a solvothermal route. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to characterize different phases, crystallinity, morphology and vibrational mode. Magnetic properties were investigated by a vibrating sample magnetometer (VSM). Chemical composition and valence state of the nanocomposites were analyzed by X-ray photoelectron spectroscopy (XPS), including energy band gap was determined by diffuse reflectance UV–visible spectroscopy. The MZF@SiO 2 /BiOBr 0.5 Cl 0.5 nanocatalyst has strong adsorption in the dark and high photocatalytic performance in degrading of rhodamine B (RhB) dye under visible light irradiation. At the end of the fourth re-cycle, removal of 30 μM RhB solution was ~80% and the recycled photocatalyst separated by external magnetic field was 90 wt% of the original. In this research, calculated valence and conduction band edges were used to explain photodegradation mechanism of the MZF@SiO 2 /BiOBr 0.5 Cl 0.5 nanocomposites. [ABSTRACT FROM AUTHOR]

In this work, the synthesis and characterization of cobalt ferrite nanoparticles (CoFe2O4 NPs) were carried out. The characterization studies confirmed that the synthesized particles were determined to be magnetic CoFe2O4 NPs in nanoscale and cubic spinel structure. The Brunauer-Emmett-Teller specific surface area of mesoporous CoFe2O4 NPs was determined to be 145.03 m2/g. The photo Fenton-like degradation ability of CoFe2O4 NPs was also evaluated and the results demonstrated that the synergistic effect of combining of Co and Fe2O4 enabled CoFe2O4 NPs to become the promising photo Fenton-like catalyst for degradation of methylene blue (MB) from aqueous solutions. At the optimum experimental conditions (3.0 of initial pH, 25 mM of H2O2 concentration, 50 mg/L of initial dye concentration, and 0.25 g/L of catalyst concentration), 18.29% chemical oxygen demand removal and 99.75% color removal were achieved after the photo Fenton-like degradation of MB in the presence of CoFe2O4 NPs heterogeneous catalyst with near-UV radiation. [ABSTRACT FROM AUTHOR]

A series of morphology-selected copper ferrite (CuFe 2 O 4) anode materials for sodium ion batteries were firstly prepared via a highly efficient spray drying method using glycine as the complex and accelerator. It was found that the glycine/nitrate (G/N) molar ratio has an important influence on the crystallinity, morphology and electrochemical properties of sodium storage. Compared with the other prepared materials, the G/N-0.3 (glycine-nitrate molar ratio of 0.3) exhibits the most excellent electrochemical performance. The excellent electrochemical properties can be attributed to the optimized molar ratio of glycine-nitrate, which induce a good crystallinity with a proper porous structure, thereby improving the cycle life of the battery. [ABSTRACT FROM AUTHOR]

Synthesis of Zn–Mn ferrite from spent Zn–Mn batteries using a multi-step process of bioleaching and co-precipitation represents a promising means in waste management of the spent batteries. However, the low pulp density of 1.0% in bioleaching process means a low yield of Zn–Mn ferrite. In this work, the cheap and benign Fe3+ was used to replace dangerous H 2 SO 4 or expensive Cu2+ to promote bioleaching performance of spent batteries at a high pulp density of 5.0% for synthesis of Zn–Mn ferrite for the first time. The results displayed the addition of Fe3+ greatly enhanced bioleaching of spent batteries. The extraction efficiency of Zn and Mn increased from 34.5% to 29.4% to the maximum of 85.1% and 83.2%, respectively, when the concentration of added Fe3+ increased from 0 to 5.0 g/L. The added Fe3+ motivated more generation of both Fe2+ and sulfur to promote the growth of both Leptospirillum ferriphilum and Acidithiobacillus thiooxidans , respectively, attaining a higher bioleaching rate. The electro - chemical analysis also revealed the highest J Corr of 0.571 mA cm−2 occurred when the concentration of added Fe3+ was 5.0 g/L. The addition of Fe3+ at 5.0 g/L witnessed the maximum synthesis yield of Zn–Mn ferrite (52.6 g/L). • Added 5.0 g/L Fe3+ lifts bioleaching rate of Zn and Mn from 30% to over 80%. • Added Fe3+ saw more generation of Fe2+ and S0 to promote growth of L.f and A.t. • When added Fe3+ lifted from 0 to 5.0 g/L, J Corr rose from 0.190 to 0.571 mA cm−2 • Remaining Fe3+ had no negative effect on the synthesis of Zn–Mn ferrite. • Addition of 5.0 g/L Fe3+ witnessed maximum yield of Zn–Mn ferrite (52.6 g/L). [ABSTRACT FROM AUTHOR]

• Cobalt ferrite was synthesized via the sol-gel method with varying precursor stoichiometries. • Cation in excess shows a marked preference towards the octahedral site. • A very uncommon normal spinel configuration was observed for CoFe 2 O 4. • The Curie point of the extreme formulations differ by almost 100 °C. Spinel cobalt ferrites (CoFe 2 O 4) with varying inversion degrees were prepared via a citrate-nitrate sol-gel method. The gels, prepared with different cation stoichiometries, were dried at 110 °C, further treated at 850 °C and subjected to structural and magnetic characterization. X-ray diffractograms of the samples confirm the successful synthesis of the spinel. The synthesis conditions displayed a strong influence over the positioning of the cations in the crystal structure of these ferrimagnets. Mössbauer spectra yield inversion degrees of approximately 1.0 and 0.0 for the samples prepared with excess cobalt and excess iron, respectively. These cationic arrangements are also confirmed via Raman spectroscopy, which shows a larger splitting of the A 1g signal in the sample with the highest inversion degree. The magnetic character of the samples at room temperature does not agree with what should be expect from the net magnetic moments per unit cell. However, this phenomenon was explained by the different exchange integrals at play in each of the systems, as shown by the magnetic critical temperature of each arrangement, which differed by approximately 100 °C. The proposed pathway has proven to be an accurate method for completely switching the cationic arrangement of CoFe 2 O 4 , further enabling the application of this material in advanced magnetoresistive and spintronic devices. [ABSTRACT FROM AUTHOR]

Cobalt, nickel and zinc nanosized spinel-type ferrites (MFe 2 O 4 , M: Co2+, Ni2+ and Zn2+) were synthesized by the novel oil-in-water microemulsion method. These compounds have not been fully studied for H 2 production by the water-splitting reaction, especially those prepared by microemulsion. Through proper characterization, features like crystal structure, efficient visible light absorption, high-sorption capacity and adequate textural properties, were demonstrated for thermal treated Co, Ni and Zn microemulsion synthesized nanoferrites. These characteristics favored the visible light-driven H 2 production (monitored by gas chromatography) of MFe 2 O 4 nanoparticles dispersed in water (2% MeOH), under experimental conditions. Particularly, ZnFe 2 O 4 yielded a higher amount of H 2 (354 μmolH 2 g−1) compared to Co (128 μmolH 2 g−1) and Ni (129 μmolH 2 g−1) ferrites in an 8 h experiment, presumably due to more favorable electronic band positions. This work represents a new contribution to the hydrogen evolution studies using ferrite nanoparticles. • Crystalline spinel-type ferrites (MFe 2 O 4) nanoparticles were synthesized by the oil-in-water microemulsion method. • MFe 2 O 4 nanoparticles exhibited good photocatalyst features in terms of structure, size, surface area and optical bandgap. • MFe 2 O 4 nanoparticles are molecular hydrogen producers at studied conditions. • ZnFe 2 O 4 yielded a higher H 2 production compared with cobalt and nickel ferrites. [ABSTRACT FROM AUTHOR]

Highlights • M-type hexaferrite BaZn 0.6 Sn 0.6 Fe 10.8 O 19 was synthesized at a low sintering temperature of 900 °C. • Rietveld refinement were adapted to make investigated parameters more standard. • This M-type hexaferrite is potential candidate for the design of microwave devices such as circulator operated at Ku band. Abstract M-type barium hexaferrite (BaM) of composition BaZn 0.6 Sn 0.6 Fe 10.8 O 19 was successfully synthesized through a ceramic process. Sintering aids Bi 2 O 3 ·B 2 O 3 ·SiO 2 ·ZnO (BBSZ) were added to lower the sintering temperature. The formation of pure M phase for samples sintered at 900 °C with sufficient BBSZ was confirmed from XRD patterns analysis. Large saturation magnetization (69.02 emu/g) and relatively low magnetic anisotropy field (7.4 kOe) were obtained simultaneously when sample was synthesized with 2.5 wt% BBSZ dosage. These properties make the material suitable for applications in LTCC process. The ferromagnetic resonance (FMR) linewidth (Δ H) decreased efficiently by 719 Oe owing to the sintering aids. This M-type hexaferrite is also potential candidate for the design of microwave devices such as circulators and isolators operated at low frequencies. Meanwhile, the influences of sintering aids upon the microstructure, complex permeability and magnetic properties of M-type hexaferrite BaZn 0.6 Sn 0.6 Fe 10.8 O 19 were investigated. [ABSTRACT FROM AUTHOR]

Highlights • Cation distribution was determined in 10-nm sized Mn 0.6 Zn 0.4 Fe 2 O 4 particles. • Small clusters of Mn-Zn ferrite crystallites were coated with mesoporous silica. • The mesoporous shell was loaded with rhodamine B as a hydrophilic model compound. • The shell was sealed by a temperature-sensitive gatekeeper to control the release. Abstract Hydrothermal synthesis was employed to prepare three samples of Mn-Zn ferrite nanoparticles with the mean size of crystallites of 12–14 nm, whose compositions were accurately determined by X-ray fluorescence spectroscopy to Mn 0.82 Zn 0.21 Fe 1.97 O, Mn 0.70 Zn 0.31 Fe 1.99 O 4 , and Mn 0.62 Zn 0.41 Fe 1.97 O 4. The X-ray diffraction and SQUID magnetometry were used to determine the spinel structure and ferrimagnetic properties of the samples. AC field heating experiments were performed on particles dispersed in glycerol to evaluate the specific absorption rate. Based on the superparamagnetic behaviour and magnetic hyperthermia data, the Mn 0.62 Zn 0.41 Fe 1.97 O 4 phase was selected for further studies, including a more detailed characterization of the crystal and magnetic structure by neutron diffraction and Mössbauer spectroscopy, encapsulation into mesoporous silica, determination of the specific absorption rate of coated particles, and analysis of the porosity of the shell. Shortly, the Mn 0.62 Zn 0.41 Fe 1.97 O 4 nanoparticles were found to possess high magnetization of M (10kOe) = 48.4 emu/g at room temperature and superparamagnetic behaviour at body temperature on the timescale of magnetic measurements. The coated product was formed by clusters of ferrite crystallites with overall mean size of 52 nm encapsulated into 22 nm thick mesoporous shell and showed heating efficiency of 57 W/g(Mn + Fe) in AC field of 970 kHz and amplitude of 8 mT. The mesoporous shell provided specific surface area of 670 m2/g, and its pores of an average diameter 3 nm occupied specific volume of 0.45 cm3/g. In a a preliminary study, the silica pores were loaded with rhodamine B as a model of a hydrophilic drug and subsequently enclosed by lauric acid that served as a temperature sensitive gatekeeper. The release of the model compound to aqueous medium was determined at room temperature and 60 °C by spectrophotometric analysis. Results have shown that amount of rhodamine B in pores achieved 15 mg per gram of silica-coated ferrite cores and its release was controlled by temperature. [ABSTRACT FROM AUTHOR]

Highlights • Synthesis of monophase Mn-ferrite nanoparticles (NPs) via the hydrothermal method. • Applying of polyethylene glycol (PEG) polymer as a coating on the synthesized NPs. • Improving stability of dispersions containing the PEG-coated Mn-ferrite NPs at pH 7. • Superparamagnetic PEG-coated Mn-ferrite NPs with enhanced MRI contrast effect. Abstract In this work, manganese ferrite (MnFe 2 O 4) nanoparticles (NPs) were successfully synthesized via the hydrothermal method, and the dispersibility and the biocompatibility of the product were improved by the polyethylene glycol (PEG) polymer as a coating onto the surface of the synthesized NPs. The potential of the use of the synthesized PEG-coated NPs as contrast agents in the magnetic resonance imaging (MRI) was also investigated. The XRD results showed that the monophase MnFe 2 O 4 NPs were synthesized at the pH of 11, the temperature of 200 °C for 12 h (optimal conditions) via the hydrothermal method. The FE-SEM and TEM investigations showed that the hydrothermally synthesized NPs had a quite homogeneous size distribution with the average size of about 50 nm. The water-based dispersions of PEG-coated Mn-ferrite NPs showed the higher stability at pH 7 in comparison with the uncoated ones. The PEG-coated Mn-ferrite NPs showed a high saturation magnetization value (60 emu/g). An enhanced MRI contrast effect by the PEG-coated NPs was confirmed via the in vitro MRI study. Moreover, the cytotoxicity activity of the PEG-coated NPs on the HeLa cells demonstrated a high cell viability even at a 0.2 mg/ml of NPs after 48 h of incubation. Also, the in vitro hemocompatibility studies of the synthesized NPs showed that the PEG-coated NPs had no effect on the blood coagulation factors, and the red blood cell (RBC) count measured by complete blood count (CBC) tests in all the investigated concentration range. It can be concluded that, therefore, the hydrothermally synthesized PEG-coated Mn-ferrite NPs in this study can be good candidates as MRI contrast agents. [ABSTRACT FROM AUTHOR]

Abstract Co-Mg ferrites, Co x Mg 1 − y Fe 2 − z O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, 0 < y < 0.34 and 0 < z < 0.67), were synthesized via a standard ceramic route, and the structural, morphological, magnetic properties and transmission parameter of the samples were studied. The thermal behavior of the ground powder was characterized using a differential thermal analysis technique (DTA). The XRD patterns proved the formation of single phase Mg-ferrite in the samples with "x" contents varying from 0.0 to 0.8. The sample with x = 1.0 showed two phases: a spinel Mg-ferrite and a secondary (Co,Mg)O phase. The lattice parameter and crystallite size of the samples increased remarkably by increasing the x content. The SEM images revealed that Co substitution in Mg ferrite at x = 0.2 causes the particle growth, but their growth was not significant until x = 0.8. For x = 1.0, a remarkable particle growth was again observed. A maximum bulk density of 4.94 g/cm3 was obtained for x = 0.8. Magnetic properties of the sintered samples showed an increase in coercive force up to 113 Oe by increasing Co substitution up to x = 1.0. Saturation magnetization reached a maximum value of ~45.40 emu/g at x = 0.8. Studying the microwave transmission behavior of the samples, using a vector network analyzer (VNA), indicated that by increasing Co, the transmission loss was reduced from ~ − 15 dB for x = 0.0 to less than − 10 dB for x = 0.8 in the frequency range of 8–12 GHz. [ABSTRACT FROM AUTHOR]

Highlights • Magnetic and microwave absorption analysis of Ba (1−2x) La x Na x Fe 10 Co 0.5 TiMn 0.5 O 19. • Saturation magnetization decreases from 55.667 to 44.768 emu/g for x = 0.00 to 0.25. • RL for the sample x = 0.10 is −45.94 dB (99.997% absorption) with 8.33 GHz bandwidth. • Synthesized ferrites can be utilized in EM shielding and RAM applications. Abstract La-Na co-substituted M-type Co-Ti-Mn barium hexaferrites Ba (1−2x) La x Na x Fe 10 Co 0.5 TiMn 0.5 O 19 (0.00 ≤ x ≤ 0.25) were synthesized by conventional solid-state method. The influence of La-Na doping on the magnetic properties was investigated through VSM (vibrating sample magnetometer). The room temperature hysteresis loops show that the saturation magnetization decreases from 55.667 emu/g for x = 0.00 to 44.768 emu/g for x = 0.25 sample. To determine the complex permittivity (ε r = ε′ – iε″) and permeability (µ r = µ′ – iµ″) in 18.0–26.5 GHz frequency range, a vector network analyzer was employed. Reflection loss (RL) values were simulated from the values of ε r and µ r acquired using transmission line theory. The minimum RL obtained for the sample x = 0.10 is −45.94 dB (99.997% signal absorption) with an absorption bandwidth of 8.33 GHz for 1.3 mm sample thickness. Thus, the synthesized hexaferrites can be utilised in electromagnetic shielding and radar stealth technology applications. [ABSTRACT FROM AUTHOR]

Graphical abstract The tetraalkyliron(III) complex, [Li(THF) 2 ][Fe(CH 2 Si(CH 3) 3) 4 ], has been synthesized containing modified methylene substituents that incorporate large trimethylsilyl (TMS) groups to further probe steric and electronic ligand effects in tetraalkyliron(III) complexes by increasing the electron-donating ability of the ligand while retaining steric bulk. Detailed structural and DFT studies provide insight into electronic structure and bonding of this complex compared to the previously reported analogs containing methyl and benzyl ligands. Abstract Homoleptic iron-alkyl complexes have been implicated as key intermediates in iron-catalyzed cross-coupling with simple iron salts. Tetraalkyliron(III) ferrate species have been shown to be accessible with either methyl or benzyl ligands, where the former complex is S = 3/2 and distorted square planar while the latter is a S = 5/2 distorted tetrahedral species. In the current study, a new tetraalkyliron(III) complex is synthesized containing modified methylene substituents that incorporate large trimethylsilyl (TMS) groups to further probe steric and electronic ligand effects in tetraalkyliron(III) complexes by increasing the electron-donating ability of the ligand while retaining steric bulk. Detailed structural and DFT studies provide insight into electronic structure and bonding of the four-coordinate trimethylsilylmethyl iron(III) complex compared to the previously reported analogs containing methyl and benzyl ligands. [ABSTRACT FROM AUTHOR]

Abstract The additional effect of the dynamic strain aging (DSA) on the microstructural parameters in influencing the yield strength was analyzed through comparing the difference between the experimental yield strength and the calculated value at room temperature (RT) in 9Cr-1.7W-0.1C reduced activated ferritic-martensitic (RAFM) steel samples treated under two different heat treatments. Different heat treatments leaded to the variation of the microstructural parameters of this steel. Then the contributions of these microstructural parameters and DSA on the tensile properties at elevated temperatures were studied with the modified Crussard–Jaoul (C–J) analysis based on the Swift equation. [ABSTRACT FROM AUTHOR]

Abstract Oxide dispersion strengthened (ODS) steels of Fe–9Cr– x Al (x = 0.4, 2.5, 4.5 and 8.0 wt%) have been fabricated by mechanical alloying, hot isostatic pressing and subsequent forging. Both the ferrite matrix and yttria particles were coarsened by the addition of Al. However, a bimodal structure consisting of coarse grains closely surrounded by fine grains is formed, and develops with increasing Al addition. Moreover, at the same time, nano-sized alumina particles precipitate in the interior of the bimodal ferrite grains. The tensile strength increases gradually with Al addition due to back stress strengthening combined with Orowan strengthening. The formation mechanism of the bimodal structure and intragranular precipitation of the Al added ODS steels were also discussed. [ABSTRACT FROM AUTHOR]

Abstract Metal-doped magnesium ferrite (MgFe 2 O 4) with cubic spinel structure, large specific surface area and medium saturation magnetic strength was synthesized from saprolite laterite leaching solution through hydrothermal-calcination method and used as a heterogeneous Fenton-like catalyst. The influence of reaction temperature on the catalytic process was centrally discussed based on the hydroxyl radical theory. The as-prepared MgFe 2 O 4 exhibited favorable catalytic activity for degradation of Rhodamine B (RhB), achieving 97.8% degradation efficiency of 10 mg·L−1 RhB within 300 min (90.0% degradation, 180 min) at the conditions of 45 °C, pH 6.44, 0.625 g·L−1 catalyst dosage and 1.00 vol% H 2 O 2 concentration. And the TOC removal efficiency could reach 77.8%. After five consecutive degradation cycles, the reduction of degradation and TOC removal efficiencies were <3.0% and 8.0%, respectively, suggesting the metal-doped MgFe 2 O 4 had high catalytic activity, good stability and excellent reusability. More importantly, the formed catalyst may broaden the application of saprolite laterite and provide a promising way for other natural minerals which contain transition metal elements in the treatment of organic dye wastewater. Graphical abstract Metal-doped magnesium ferrite synthesized from saprolite laterite is an effective and stable heterogeneous Fenton-like catalyst for organic dye removal. Unlabelled Image Highlights • Metal-doped MgFe 2 O 4 was synthesized from saprolite laterite. • The as-prepared MgFe 2 O 4 is an effective heterogeneous Fenton-like catalyst. • The rise of temperature could promote the formation of OH radicals in as-prepared MgFe 2 O 4 /H 2 O 2 system. • The catalyst exhibited high stability and excellent reusability. [ABSTRACT FROM AUTHOR]

Abstract Spinel and garnet nanostructured ferrites have been used for various potential applications. Single phase spinel and garnet nanoferrites have been used for different applications in many fields. Ni-Zn (Ni 0.5 Zn 0.3 Al 0.2 Fe 2 O 4) ferrite with spinel structure and YAIG (Y 2.8 Al 0.2 Fe 5 O 12) ferrite with garnet structure were synthesized using sol-gel technique. The structural, morphological and magnetic studies were done for spinel and garnet nanoferrites. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were used to investigate the structural, morphological and magnetic properties of the spinel and garnet nanoferrites respectively. Single phase spinel and garnet nanocrystalline ferrites were confirmed from XRD analysis. Circular and cubic shape morphology was observed for spinel and garnet nanoferrites respectively. Static magnetic characteristics of the Al doped spinel and garnet nanoferrites (saturation, remanence, coercivity and magnetic squareness) were measured from the hysteresis loops. Dynamic magnetic properties such as initial permeability, Q factor and magnetic losses of the Al doped spinel and garnet nanoferrites were also evaluated from magnetic measurements. Spinel and garnet nanoferrites prepared at low temperature may have potential in industrial and technological applications e.g. transformers, switching, cores, filters, sea bed logging, MLCI's, microwave absorption bio medical applications and microwave frequency (C and X) band applications. Graphical abstract Image 1 Highlights • Ni 0.5 Zn 0.3 Al 0.2 Fe 2 O 4 and Y 2.8 Al 0.2 Fe 5 O 12 ferrites were synthesized using sol-gel technique. • Circular and cubic shape morphology was observed for spinel and garnet nanoferrites respectively. • Better magnetic characteristics are achieved for Al doped garnet nanoferrites. • These are suitable for MLCI's and microwave frequency (C and X) band applications. [ABSTRACT FROM AUTHOR]

Abstract For the first time, Manganese ferrite (MnFe 2 O 4) with two different catalytic and morphological properties were synthesized through the conventional and template-synthetic approaches. The typical conventionally prepared MnFe 2 O 4 particles attained nanoscaled spherical structure, and the unique structured novel MnFe 2 O 4 nano-agglomerates were conquered by the template synthesis. The templates of MnCO 3 made MnFe 2 O 4 to attain the nano-agglomeric structure with the abundant electroactive surface area and copious catalytic sites, which were confirmed through the structural, morphological, elemental, and electrochemical investigations. By the recent reports, the supercapacitor and heavy metal detection properties of MnFe 2 O 4 were recognized. Therefore, both the MnFe 2 O 4 nanospheres (NSs), and MnFe 2 O 4 nano-agglomerates (NAs) were applied for the detection of Hg(II) ions in real samples, and also for the supercapacitor applications. Both the materials exhibited moral parameters in electrochemical sensing and supercapacitor applications, but the results obtained for the MnFe 2 O 4 NAs is quite high (LOD: 0.14 nM and Specific capacitance: 1283 F/g at 5 mV/s) when compared to the NSs. Finally, the MnFe 2 O 4 NAs was employed to be an active participant in supercapacitor and also to detect Hg(II) ions in seafood and industrial wastewater samples. Graphical abstract Image 1 Highlights • For the first time, unique structured novel MnFe 2 O 4 nano-agglomerates were conquered by the template synthetic approach. • The typically synthesized MnFe 2 O 4 nanospheres were compared with the template synthesized nano-agglomerates. • As a comparison study, both the MnFe 2 O 4 nanospheres and nano-agglomerates were applied for the detection of Hg(II) ions, and also for the supercapacitor applications. • The results obtained for the MnFe 2 O 4 nano-agglomerates is quite high (LOD: 0.14nM and Specific capacitance: 1283 F/g at 5 mV/s) on compared to the nanospheres. [ABSTRACT FROM AUTHOR]

In this study, BiFeO 3 (BFO) nanoparticles were synthesized via the sol–gel route and BFO/nitrogen-doped graphene (NG) nanocomposites (BFO/NG, NG: 1%, 2%, 3%, 4%, 5%, and 6%) were prepared by dispersing the BFO nanoparticles and NG in ethanol solution, before thermal drying. The structural and morphological properties of the pure BFO nanoparticles, NG, and BFO/NG nanocomposites were studied by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. The average crystallite size of the BFO nanoparticles was 57 nm. The SEM observations demonstrated that the BFO nanoparticles were well anchored on the NG. The photocatalytic activities of the as-synthesized samples were calculated based on the degradation of methyl orange under simulated sunlight irradiation. The BFO/NG nanocomposites exhibited enhanced photocatalytic activity compared with the pure BFO nanoparticles. The enhanced photocatalytic performance was attributed to the efficient transfer of photogenerated electrons from the BFO nanoparticles to NG, thereby leading to the increased availability of h + for the photocatalytic reaction. Furthermore, hydroxyl (⋅OH) radicals were detected using the photoluminescence technique with terephthalic acid as a probe molecule and they were generated on the irradiated pure BFO nanoparticles and BFO/NG nanocomposites. [ABSTRACT FROM AUTHOR]

Sol-gel autocombustion method using glycine as fuel and complexing agent was utilized to synthesize nanocrystalline Mg 1-x Cd x Fe 2 O 4 (x = 0–0.8) ferrites. An increase in adiabatic flame temperature with x during the combustion reaction was demonstrated, based on the thermodynamic calculations. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) results confirmed that a single-phase spinel structure in all samples is formed at a remarkably lower temperature and with a larger production rate compared to the standard ceramic and other wet-chemical methods. Crystallites growth from 98 nm to 320 nm, enhanced X-ray density and a linear increase in both theoretical and experimental lattice constants, with comparable values were observed with introduction of cadmium. Analysis of the XRD patterns, using the Bertaut method along with a detailed Rietveld analysis reflected a different cations distribution and evolution of some structural parameters with cadmium, compared to the earlier studies. The Field-emission scanning electron microscopy (FESEM) results showed that the average particle size of the synthesized ferrites increases from 161 to 520 nm for x = 0 to x = 0.8, respectively. The magnetic measurements revealed that the saturation magnetization ( M s ) initially increases and reaches the maximum value of 46 A m 2 kg −1 at x = 0.2, and subsequently decreases, while the coercivity ( H c ) and remanent magnetization ( M r ) continuously decline with x values. The present magnetic results for x = 0.0 − 0.4, show a noticeable improvement in magnetic softness compared to previous researches on the Mg-Cd ferrites obtained by other chemical methods. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of lithium ferrite nanoparticles synthesized through the solution combustion route at different fuel to oxidizer ratio are studied using different techniques. Powder X-ray diffraction studies show that the fuel to oxidizer ratio is a critical parameter that determines the phase purity and degree of order of the samples. Magnetic studies show that the saturation magnetization and coercivity are comparable to those reported for lithium ferrites prepared using other methods. Saturation magnetization of Li0.8 sample at room temperature is 60 emu/g and is close to the bulk value. The hyperfine parameters obtained from the Mössbauer spectra of Li0.6 and Li0.8 also match the reported values of phase pure samples. Mössbauer spectra of samples prepared at stoichiometric and fuel rich conditions show the presence of Fe 2+ cations in the ferrite phase, indicating that a reducing environment which reduces Fe 3+ to Fe 2+ ions is created as the fuel to oxidizer ratio is increased. The variation in the structural and magnetic properties of the samples, combined with TGA and FTIR studies, shows that the fuel lean condition is more appropriate for the direct formation of single phase lithium ferrite nanoparticles. [ABSTRACT FROM AUTHOR]

A series of paramagnetic ionic liquids (PILs) based on N , N ′-bis(alkyl)imidazolium bromotrichloroferrate(III), [(C n ) 2 Im][FeCl 3 Br] (Im = imidazole; C n  = ethyl, butyl, hexyl, octyl, decyl, dodecyl), was prepared and compared against the more traditional [C n C 1 Im][FeCl 3 Br] (C 1  = methyl) analogs. Both series were extensively characterized by physical, chemical, and computational methods including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), spectroscopy (FTIR and UV‐vis-NIR), magnetic susceptibility, surface tensiometry, density, and viscosity. The X-ray crystal structure of [(C 12 ) 2 Im][FeCl 3 Br] was also obtained. Notably, all ionic liquids prepared in this study show short-term thermal stabilities exceeding 300 °C in air and have melting points equal to or lower than 25 °C, which is surprisingly low for ionic liquids containing symmetrical cations. In addition, all presented ionic liquids have relatively low viscosities allowing for easier transitioning into applications. Physical property trends are discussed. [ABSTRACT FROM AUTHOR]

Atomistic modeling is used to investigate the energetics and structures of commonly reported orientation relationships between ferrite and cementite within pearlite: the Bagaryatskii, the Isaichev, and the Pitsch-Petch, as well as their associated near orientations. Dislocation arrays are found to form for all orientation relationships, with their spacing and direction a function of lattice mismatch. Within each orientation relationship, different interfacial chemistries are found to produce identical dislocation spacings and line directions, but differing interfacial energies. This chemistry component to the interfacial energy is characterized and it is determined that in addition to the lattice mismatch, there are two structural factors within the cementite terminating plane that affect the energetics: the presence of like site iron pairs and proximity of carbon atoms to the interface. Additionally, an alternate method for determining the interfacial energy of systems in which there are multiple chemical potentials for a single element is developed and implemented, an approach which is likely valid for other similar systems. The Isaichev orientation relationship is found to be the most favorable, while the “near” orientation relationships are found to be at least as energetically favorable as their parent orientation relationships. A continuum model based on O-lattice theory and anisotropic continuum theory was also applied to the atomistic results, yielding interfacial energy approximations that match well with those from atomistics and allowing for the characterization of the Burgers vectors, which are found to lie in high symmetry directions of the ferrite within the interface plane. [ABSTRACT FROM AUTHOR]

In this present work, series of Mg 1-x Sr x Fe 2 O 4 (x = 0.05–0.25) nanoparticles were prepared by simple chemical method and their properties were evaluated with different characterization techniques. Transmission Electron Microscope (TEM) and powder X-ray diffraction (XRD) results were strong evident for the formation of spinel structured crystalline nanoferrite. TEM and Selected Area Electron Diffraction (SAED) visible evidence for the formation of high crystalline nanoparticles. Synthesized ferrite nanoparticles exhibits normal dielectric behavior which is modified with different Sr 2+ content. The presence of grain and grain boundary in ferrite nanoparticles were identified in TEM and impedance analysis and their electrical response were controlled by different Sr composition. The Magnetic properties were measured by vibrating sample magnetometer (VSM), which showed that the synthesized particles were in ferrimagnetic state. On the substitution of comparatively large ionic size Sr 2+ in spinel structure Mg ferrite, we observed interesting electrical and magnetic properties of ferrite particles. [ABSTRACT FROM AUTHOR]

Present paper describes systematic studies of the functional BaFe 12-x DI x O 19 (DI = Al 3+ , In 3+ 0.1 ≤ x ≤ 1.2) solid solutions. Correlation between the fine atomic structure and intrasublattice Fe 3+ - O 2− - Fe 3+ superexchange interactions were explained using precision neutron powder diffraction and Mossbauer spectroscopy. Critical influence of the diamagnetic Al 3+ and In 3+ ions on electromagnetic properties in substituted Ba-hexaferrites (M-type) was discussed. Transmission spectra demonstrated a deep minimum in the frequency range 20–65 GHz due to natural ferromagnetic resonance (NFMR). Increase of the Al 3+ ions concentration shifted the resonance frequency from 51 GHz to 61 GHz. Increase of the In 3+ ions shifted the resonance frequency from 50.5 GHz to 27 GHz. Data of the numerical calculations and experimental results correlates well. It has been demonstrated that external magnetic fields critically influence on electromagnetic properties due to increase of magnetic anisotropy. This opens broad perspectives for practical applications. [ABSTRACT FROM AUTHOR]

We report the synthesis of Cu x Co 0.5-x Ni 0.5 Fe 2 O 4 with x = (0.1, 0.2, 0.3, 0.4) nanoparticles using the co-precipitation method in the presence of oleic acid as a surfactant and coating material. The X-ray diffraction analysis with Rietveld refinement technique confirmed the formation of cubic phase with Fd-3m space group of all the prepared nano-ferrites. The average crystallite size varies in the range of 21–38 nm with varying concentration of copper. The lattice parameter was found to decrease with increase in copper substitution. This may be attributed to larger ionic radius of cobalt as compared to that of copper. TEM and SEM analysis showed the monodispersion and cubic-like nanostructure. Two prominent stretching bands were observed in FT-IR spectra around 400–600 cm −1 . These two bands confirmed the spinel structure of the prepared nanoparticles. Raman spectroscopy is used to verify that we have synthesized ferrite spinels and determines their phonon modes. The thermal decomposition of Cu x Co 0.5-x Ni 0.5 Fe 2 O 4 was investigated by TGA∖DTA. The optical study UV–visible is used to calculate the optical band gap energies. The products exhibited the attractive magnetic properties with high saturation magnetization, which were examined by a vibrating sample magnetometer (VSM). On the other part, the photocatalytic activity of our compounds was studied using methylene blue (MB) as model organic pollutants, where the results showed that an appropriate amount of copper (Cu 2+ ) could greatly increase the amount of hydroxyl radicals generated by the ferrite nanoparticles, which were responsible for the obvious increase in the photocatalytic activity. [ABSTRACT FROM AUTHOR]

Development of green catalytic processes using biobased feedstock for valuable chemicals such as 5-hydroxymethylfurfural (HMF) is hotly pursued. 2, 5-Furandicarboxylic acid (FDCA), a bio-based alternative to terephthalic acid was efficiently synthesized by oxidation of HMF using MnFe 2 O 4 spinel structured magnetic nanoparticles (MNPs) and tert -butyl hydroperoxide as an oxidant. MnFe 2 O 4 catalyst showed the highest activity and selectivity and gave 85% yield of FDCA at 100 °C in 5 h. The higher activity of MnFe 2 O 4 catalyst is due to the variable oxidation state of manganese. The combination of MnFe 2 O 4 catalyst and TBHP oxidant requires less time and energy compared to other reported processes of FDCA synthesis. Also, many reported methods have used a homogeneous base for FDCA synthesis which is totally avoided in the current process. The concentration profiles of reactants and products were established and kinetics determined. The effects of various reaction parameters were studied to validate kinetic model. The catalyst was easily recycled due to its magnetic property and showed good catalytic activity up to four cycles. All metal ferrites were characterized by different analytical techniques. The catalyst maintained its fidelity. [ABSTRACT FROM AUTHOR]

Rare earth Neodymium (Nd 3+ ) doped nanocrystalline Ni-Co mixed spinel ferrites which are chemically represented as Ni 0.5 Co 0.5 Nd x Fe 2-x O 4 (x = 0.025 to 0.125, in the step of 0.025) were synthesized by sol-gel auto-combustion method. The structural, morphological, infrared and magnetic properties were studied in detail in the light of Nd 3+ doping using standard techniques. X-ray analysis reveals the formation of single phase cubic spinel structure for all the prepared samples without any impurity phase. The crystallite size calculated from Scherrer's formula was observed to be decreasing with increasing Nd 3+ content. The lattice parameter calculated using XRD data was found to be decreasing upto x = 0.100 and then increases for x = 0.125. X-ray density was observed to be increasing from 5.327 to 5.630 gm/cm 3 . Surface morphology was studied through scanning electron microscopy technique. Grain size calculated from SEM analysis was found to be in the range of 30–59 nm. From transmission electron microscopy study, the average particle size was observed to be in the range of 35–45 nm. FTIR results exhibit the characteristics cubic spinel ferrite nature of the samples with two prominent absorption bands near 400 cm −1 and 600 cm −1 . FTIR also confirms the incorporation of Nd 3+ in the crystal structure. The magnetic behavior shows strong influence of substitution of Nd 3+ ions. The saturation magnetization, coercivity and remenance magnetization all decrease with substitution of Nd 3+ ions up to x = 0.100. For further increase in Nd 3+ concentration (x = 0.125), the saturation magnetization found to be increased. [ABSTRACT FROM AUTHOR]

The V-Ti-N microalloyed steel with a carbon content gradient was innovatively obtained through surface decarburization. Then, the effect of carbon contents on intragranular ferrite (IGF) formation was studied. With the carbon contents increasing from 0.39% to 0.47% (mass percent), the volume fraction of IGF decreases from 8.2% to 4.6%, but the number of IGF has no significant change. The critical size of IGF nuclei was calculated on the basis of classic heterogeneous nucleation theory. According to the results of calculation and statistics, with the carbon content increasing from 0.39% to 0.47%, the number of IGF nuclei does not decrease significantly. When the carbon content is relatively low, some (Ti, V)(C, N) particles precipitating in austenite matrix may also act as the nuclei of IGF to refine the pearlite-ferrite microstructure. [ABSTRACT FROM AUTHOR]

Novel MnFe 2 O 4 /g-C 3 N 4 composites were successfully synthesized via a facile hydrothermal route in combination with ultrasonication and calcination techniques. XRD patterns of the as-synthesized composite furnished evidence for presence of both MnFe 2 O 4 and g-C 3 N 4 components. SEM and TEM micrographs also confirmed the successful formation of the MnFe 2 O 4 /g-C 3 N 4 composite. The catalytic efficiency of the synthesized composite was investigated in crossed aldol condensation of acetone with benzaldehyde. The results demonstrated that the condensation reaction produced dibenzylideneacetone (DBA) in excellent yields under reasonably mild conditions. Owing to the presence of g-C 3 N 4 nanosheets, MnFe 2 O 4 /g-C 3 N 4 composite exhibited a larger specific surface area and also an inherent basic characteristic. The other key feature of the composite is its easy magnetic recovery. [ABSTRACT FROM AUTHOR]

Power ultrasonic vibration was applied to the solidification of calcium ferrite (CF) melt in this study. The results indicated that power ultrasound can promote the formation of CF by accelerating the solidification process. Ultrasonic vibration greatly refined the CF grains, resulting the grain size decreased from 1893 to 437 μm. Meanwhile, ultrasonic vibration significantly enhanced the compressive strength, reduced the reduction time and improved the reducibility of CF slags. With ultrasonic treatment, the ultimate compressive strength of samples increased from 37.5 to 67.8 MPa, and the reduction time decreased from 225 to 136 min. [ABSTRACT FROM AUTHOR]

Four types of Ni-Zn based ferrites materials having the general formula Ni 0.5 Zn 0.5 Nd x Fe 2− x O 4 (0.0 ≤  x  ≤ 0.12) have been successfully synthesized by calcining oxalates in air and the influence of Nd content on the structure and magnetic properties of Ni 0.5 Zn 0.5 Nd x Fe 2− x O 4 is studied. X-ray diffraction examination confirms that a high-crystallized Ni 0.5 Zn 0.5 Nd x Fe 2− x O 4 with cubic spinel structure is obtained when the precursor is calcined at 1000 °C in air for 2 h. The substitutions of Nd 3+ ions for partial Fe 3+ ions do not change the spinel crystalline structure of MFe 2 O 4 . The incorporation of Nd 3+ ions in place of Fe 3+ ions in Ni-Zn ferrites increases the average crystallite size. Specific saturation magnetization decreases with increase in Nd content. This is because Nd 3+ ions with smaller magnetic moment preferentially fill the octahedral sites. In addition, antiferromagnetic FeNdO 3 increases with increase in Nd content. In this study, Ni 0.5 Zn 0.5 Nd 0.08 Fe 1.92 O 4 , calcined at 1000 °C, exhibits the highest magnetic moment (4.2954  μ B ) and the lowest coercivity (28.82 Oe). [ABSTRACT FROM AUTHOR]

Hollow BiFeO 3 spheres of different diameter and density have been synthesized for the first time by ultrasonic spray pyrolysis. All samples exhibited ferromagnetic properties and have record values of residual magnetization and coercive force. A correlation between the particle parameters (diameter, volumetric mass density) and magnetic properties has been established. [ABSTRACT FROM AUTHOR]

Comparative study of different PZT-based composite materials ((x)PbZr 0.52 Ti 0.48 O 3 + (1-x)CoFe 2 O 4 and (x)PbZr 0.52 Ti 0.48 O 3 +(1-x)Ni 0.7 Zn 0.3 Fe 2 O 4 (x = 0.8 and 0.9)) is presented in the frame of structural, dielectric, ferroelectric and magnetic properties. PZT and NZF/CF powders were synthesized by auto combustion technique. The composites were synthesized by mixing the appropriate amount of individual phases using conventional sintering. XRD data indicated the formation of well crystallized structure of PZT and NZF/CF, without the presence of undesirable phases. SEM micrographs revealed a uniform grain distribution of both, ferroelectric and ferromagnetic phases. Non-saturated hysteresis loops are evident in all samples due to the existence of non-ferroelectric ferrite phase. All the samples exhibit typical ferromagnetic hysteresis loop, indicating the presence of the order magnetic structure. Dielectric investigations revealed that ferrites are the main source of charge carriers, which must be of electronic origin. The activation energy of effective electrical resistivity is heavily influenced by the ferroelectric phase. [ABSTRACT FROM AUTHOR]

Polycrystalline Mg 0.25 Mn 0.25 Zn 0.5−x Sr x Fe 2 O 4 (0 ≤ x ≤ 0.20) ferrites were synthesized using the solid state reaction sintering at 1373 K and 1473 K for 4 h. The XRD patterns revealed the formation of single phase cubic spinel with Sr 2 FeO 4 and SrFe 12 O 19 as impurity phases. The decrement in the lattice parameter for Sr 2+ substituted samples is attributed to the difference in ionic radii of cations. The crystallite size decreases with increase in Sr 2+ content. Low frequency dielectric dispersion is attributed due to the Maxwell-Wagner interfacial polarization. The appearance of the peak in dielectric loss spectrum for x = 0.15 and 0.20 at 1373 K and x = 0.20 at 1473 K suggests the presence of relaxing dipoles. The loss peak shifts towards lower frequency side with Sr 2+ content at 1373 K which is due to the strengthening of dipole–dipole interactions. The complex impedance spectra clearly revealed that the both grain and grain boundary effects on the electrical properties. A complex electric modulus spectrum indicates that a non-Debye type of conductivity relaxation exists. The saturation magnetization and remanence gradually decreases with Sr 2+ substitution which may be due to the existence of non-magnetic phase in the space between the magnetic particles and the substitution of Zn 2+ cation in Mg 0.25 Mn 0.25 Zn 0.5 Fe 2 O 4 ferrite lattice by Sr 2+ content. The permeability decreases significantly while the cut-off frequency increases with the Sr 2+ content at 1373 K and decreases at 1473 K, obeying the Snoek's law. The decrease in permeability with Sr 2+ content is attributed due to the decrease in magnetization because non-magnetic ions weaken the inter-site exchange interaction. [ABSTRACT FROM AUTHOR]

Strontium hexagonal ferrites with compositional formula Sr 0.85 La 0.15 (NiZr) x Fe 12-2x O 19 , where ‘x’ varies from 0.00 to 1.00 in steps of 0.25, were synthesized by auto-combustion method. Structural, magnetic, electromagnetic and microwave absorption properties of synthesized ferrites were studied. The vector network analyzer (VNA) was used to measure complex permittivity (ε′–jε′′) and complex permeability (μ′–jμ′′) in X-band (8–12.4 GHz) and Ku-band (12.4–18 GHz) frequency range. The minimum reflection loss curves were obtained using back metal plate method for analyzing absorption properties of the material. All the synthesized ferrites show maximum absorption in Ku-band for sample thickness in the range of 1.6–1.68 mm. These newly synthesized ferrites have great potential to be used as thin microwave absorber sheets with minimum reflection loss values in the range of –19.69 dB to −27.8 dB and bandwidth in the range of 680 MHz–1.25 GHz. [ABSTRACT FROM AUTHOR]

A method for solving the current challenges in manufacturing hetero-laminated material systems using Low Temperature Co-firing Ceramics (LTCC) technique is introduced in this paper. The system contains all three major materials that widely used in the LTCC industry, Zn 2 SiO 4 ceramic, NiCuZn ferrite and silver. Previous reported methods either involve additional buffer layers which would increase the device thickness, or apply mechanical pressure during the co-firing which is not compatible to the standard LTCC process. Our method provides a facile route to manufacture hetero-laminated material systems that demands no buffer layer and follows the standard LTCC process. In this paper, four glass-free hetero-laminated material systems using LTCC technology, i.e. NiCuZn/Zn 2 SiO 4 /NiCuZn/Zn 2 SiO 4 /NiCuZn (termed “LTCC-5”), NiCuZn/Zn 2 SiO 4 -Ag/NiCuZn (termed “LTCC-3-NZAN”), NiCuZn/Ag/NiCuZn (termed “LTCC-3-NAN”) and NiCuZn/Zn 2 SiO 4 /NiCuZn (termed “LTCC-3-NZN”), have be were designed, manufactured and characterized. The shrinkage rates of these material systems show well-matched temperature spectrum. The sintering properties and interfacial diffusions of the material systems were characterized using optical microscopy, electron microscopy and Energy Dispersive Spectrometer (EDS) element mapping. Optical microscopy shows that all the material systems have well-defined multi-layered structure with controllable and tunable layer thickness. Electron microscopy images prove no microstructural cracks or defects at any of the hetero material interfaces. EDS analysis further proves that the inter-diffusions of the magnetic elements (Fe and Ni) at the NiCuZn/Zn 2 SiO 4 interface is minimized. Such property is essential for achieving high performance devices for applications such as power inductors and DC/DC converters. [ABSTRACT FROM AUTHOR]

Cu 2+ substituted Mg – Zn nanoferrites is synthesized by low temperature fired sol gel auto combustion method. The spinel nature of nanoferrites was confirmed by lab x-ray technique. Williamson – Hall (W-H) analysis estimate the average crystallite size (22.25–29.19 ± 3 nm) and micro strain induced Mg 0.5 Zn 0.5- x Cu x Fe 2 O 4 (0.0 ≤ x ≤ 0.5). Raman scattering measurements confirm presence of four active phonon modes. Red shift is observed with enhanced Cu concentration. Dielectric parameters exhibit a non – monotonous dispersion with Cu concentration and interpreted with the support of hopping mechanism and Maxwell-Wagner type of interfacial polarization. The ac conductivity of nanoferrites increases with raising the frequency. Complex electrical modulus reveals a non – Debye type of dielectric relaxation present in nanoferrites. Reactive impedance ( Z″ ) detected an anomalous behavior and is related with resonance effect. Complex impedance demonstrates one semicircle corresponding to the intergrain (grain boundary) resistance and also explains conducting nature of nanoferrites. For x  = 0.2, a large semicircle is observed revealing the ohmic nature (minimum potential drop at electrode surface). Dielectric properties were improved for nanoferrites with x  = 0.2 and is due to high dielectric constant, conductivity and minimum loss value (∼0.009) at 1 MHz. [ABSTRACT FROM AUTHOR]

Manganese nanoferrites (MnFe 2 O 4 ) were synthesized via thermal decomposition method using metal organic precursors in organic solvent. The structural and optical properties of the nanoparticles were investigated using X-ray diffraction (XRD), Field emission gun scanning electron microscopy (FEG-SEM), Fourier transform infrared (FTIR) spectroscopy and Ultraviolet visible spectrophotometer (UV–Vis). Electrochemical performance of MnFe 2 O 4 was evaluated using cyclic voltammetry (CV). The voltammograms were obtained using Pt as the working electrode within a potential range of −0.5 to +0.5 V at a scan rate of 50 mVs −1 . The electrochemical behavior of the nanoferrites were studied in different electrolytes such as acidic, basic and phosphate buffer (PBS). The CV profile clearly indicates that the capacitive behavior of nanoferrites changes with change in electrolyte media. The results obtained from this study will be useful for the further applications such as magnetic materials, semiconductors, sensors and energy storage devices. [ABSTRACT FROM AUTHOR]

Passivation of anode is a main challenge in the electrochemical synthesis of ferrate(VI) (Fe VI O 4 2− , Fe(VI)). A series of electrochemical approaches were employed including polarization curve, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) to analyze the physicochemical processes involved in electrochemical synthesis of Fe(VI) using sponge iron and cast iron anodes. The results demonstrate that the sponge iron anode achieved higher yield of Fe(VI) compared to grey cast iron anode. The optimum condition to generate Fe(VI) using sponge iron was 35–50 °C and 30 mA/cm 2 . Significantly, the sponge iron anode could generate Fe(VI) for a long duration (>10 h) under these conditions; possibly suitable for large scale synthesis of Fe(VI). The prepared Fe(VI) solution was used to treat antibiotic (sulfamethoxazole (SMX)) and pesticide (atrazine (ATZ)) in water. At a molar ratio of Fe(VI) to SMX as 20:1 in the pH range from 5.0 to 9.0, almost complete oxidative transformation of SMX could be obtained. Comparatively, oxidative transformation of ATZ was incomplete (∼70%) even when [Fe(VI)]:[ATZ] = 87 at pH 5.0–9.0. Fluorescence spectra and cytotoxicity studies suggest that the oxidative transformation products of both SMX and ATZ possess lower toxicity than the parent antibiotic and pesticide, respectively. [ABSTRACT FROM AUTHOR]

Ca 2+ doped Sr 0.45- x Ca x La 0.55 Fe 11.6 Co 0.4 O 19 ( x = 0, 0.15, 0.3, and 0.45) ferrites were fabricated through a conventional ceramic process. The influences of Ca 2+ doping on the microstructure and magnetic properties of ferrites were investigated. Ca 2+ doping could mitigate the presence of impurity phase (CoFe 2 O 4 ) in ferrites. Single phase M-type ferrites could be fabricated when x ≥ 0.3. Additional Co 2+ ions entered the crystal lattice and preferentially occupied the 4f 2 site with Ca 2+ doping. This effect greatly improved the remanence (B r ) and intrinsic coercivity (H cj ) when x increased from 0 to 0.3. The average grain size of sintered ferrites slightly increased with the amount of doped Ca 2+ ions. This behavior led to the deterioration of H cj when x increased from 0.3 to 0.45. Consequently, ferrite prepared with x = 0.3 presented the highest maximum energy product ((BH) max ) of 5.24MGOe. This performance is much higher than that of conventional La-Co substituted Sr-ferrites. [ABSTRACT FROM AUTHOR]

We prepared ferrites doped with different rare earth elements (La, Ce, Sm, Gd, Dy) by ball-milling the oxides of these metals and using double sintering technique. The so-prepared ferrites have been first characterized by X-ray diffraction. We investigated the effect of rare earth doping on the spinel structure. The substituted rare earth ions, which are larger than the pristine ions, cause a different amount of distortion in the octahedral and tetrahedral sites of the ferrite lattice, which is correlated with their different size. This distortion in the spinel lattice induces different polarization effects when the materials are hit by incident electromagnetic radiation. The vibrational response of the prepared materials has been investigated by means of Raman and FTIR spectroscopy. The collected spectra show the fundamental modes as predicted by factor group theory. The dependency of Raman shift on rare earth doping affects the optical and magnetic properties of the material. [ABSTRACT FROM AUTHOR]

Zn-Sn co-substituted M-type hexaferrite with compositions of Ba(ZnSn) x Fe 12−2x O 19 (x = 0–1.2 in step of 0.2 and x = 1.0–1.2 in step of 0.04) were synthesized via a solid reaction method. Pure M phase was observed by XRD analysis for all samples. With increase of substitution contents, morphological features exhibited a shrinkage tendency in grain size. Meanwhile, the structure of samples also became more homogeneous and compact due to the enhancement of samples’ densities ( ρ ). In terms of magnetic properties, the saturation magnetization ( M s ) decreased slightly from 57.62 emu/g to 45.57 emu/g as x increased from 0 to 1.0, and then it reduced sharply to 26.23 emu/g when x reached to 1.2, which might be attributed to occupancies of partial Zn 2+ ions on 2b sublattice. The Curie temperature ( T c ) decreased remarkably from 432 °C to 230 °C. Moreover, oriented BaM with a high squareness ratio (0.81) was achieved to match the applications in microwave devices. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, are very convenient precursors with a tunable flexibility toward multifunctional nanomaterials, especially in energy storage. Typical methods to improve lithium storage are to introduce additional or self-generating carbonaceous supports to LDH-derived transition metal oxides as anode nanomaterials which can host lithium mainly though a conversion mechanism. Here, we describe a preparation of mesoporous spinel ferrite composite (MgFe 2 O 4 /ZnFe 2 O 4 ) for lithium storage, which is assisted by a combined conversion and alloying mechanism. The composite is derived by a thermal decomposition of a scalablely produced single-resource precursor of ternary Mg 2+ Zn 2+ Fe 3+ -layered double hydroxide (Mg 2+ Zn 2+ Fe 3+ -LDH), and subsequent selective etching. Electrochemical test shows that the electrode delivers an exceptional electrochemical performance, i.e., a reversible capacity of 1190 mA h g −1 after 100 cycles at 100 mA g −1 , and, in particular, a reversible capacity of 981 mA h g −1 at 500 mA g −1 after 330 cycles, as well as a reversible capacity of 541 mA h g −1 at 2000 mA g −1 after 1000 cycles. The high electrochemical performance could be attributed to the following features: the combined alloying and conversion mechanisms of ZnFe 2 O 4 , synergistic MgFe 2 O 4 , and slight-content MgO as a non-active matrix, as well as an appropriate specific area and mesoporous size distribution. Our results show that the cation-tunable LDH precursor-derived synthesis route might be an alternative to prepare multiple-component composites of spinel ferrites and transition metal oxides. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Al 3+ substitution on the electrical and dielectric properties of Ni 0.25 Cu 0.20 Zn 0.55 Al x Fe 2-x O 4 ferrites with x = 0.0, 0.05. 0.10, 0.15 and 0.20, synthesized by solid state reaction has been reported. Using two probe method, the DC resistivity has been investigated in the temperature range from 30 °C to 300 °C. Activation energy was calculated from the Arrhenius plot. The electrical conduction is explained on the basis of the hopping mechanism. The frequency dependent dielectric properties of these spinel ferrites have been studied at room temperature by measuring AC resistivity, conductivity ( σ ac ), dielectric constant and dielectric loss tangent (tan δ ) in the frequency range between 1 kHz and 120 MHz. The study of dielectric properties showed that the dielectric constant and dielectric loss increased with increasing non-magnetic Al ions. The dependence of dielectric constant with frequency has been explained by Maxwell-Wagner interfacial polarization. Cole-Cole plots show semicircular arc(s) for the samples, and equivalent RC circuits have been proposed to clarify the phenomena involved therein. The analysis of complex impedance spectroscopy has been used to distinguish between the grain and grain boundary contribution to the total resistance. [ABSTRACT FROM AUTHOR]

The magnetic and electromagnetic properties of nanocrystalline spinel ferrites with chemical formula Mg x Cd 1−x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) prepared by oxalate co-precipitation method under microwave sintering technique were studied. The magnetic and dielectric parameters of ferrites were determined by using vibrating sample magnetometer (VSM) and vector network analyzer (VNA) respectively. Magnetic parameters such as saturation magnetizations (M s ), coercive force (H c ), remnant magnetization (M r ), Yafet-Kittel (Y-K) angle of ferrites were determined from hysteresis loops. The variation of real permittivity (ε′), dielectric loss tangent (tanδ e ), real permeability (µ′) and magnetic loss tangent (tanδ m ) with frequency and Mg 2+ content were studied in X-band frequency range. The values of ε′, tanδ e , µ′ and tanδ m of ferrites were observed to be in range of 4.2 – 6.12, 2.9 × 10 −1 – 6 × 10 −2 , 0.6 – 1.12 and 4.5 × 10 −1 – 2 × 10 −3 respectively for the prepared compositions. The study of variation of reflection loss with frequency of all ferrites shows that ferrite with magnesium content x = 0.4 can be potential candidate for microwave applications in X-band. [ABSTRACT FROM AUTHOR]

Ni 0.5 Sn 0.5 Co x Mn x Fe 2−2x O 4 ferrites with x = 0.0–0.8 have been prepared by the micro-emulsion method, using CTAB as a surfactant material. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and vibrational sample magnetometer (VSM) were used to investigate the effects of Co and Mn substitutions on cationic distribution, crystallite size, lattice constant, spectral, magnetic and dielectric properties. Lattice constant and crystallite size were found to increase from 7.4 to 9.25 Å and from 11.8 to 19.7 nm respectively with increasing substitution of Co and Mn ions. Saturation magnetization (M S ) gradually increased from 20.5 to 47.6 emu/g with increase in the value of x. However, Coercivity increased from 152.7 to 462.4 Oe up to x = 0.4 and then it decreased thereafter. The dielectric constant, complex dielectric constant and tan loss (tanδ) were observed to decrease with increase in frequency, depicting the semiconductor behavior of the ferrites. Dc resistivity was observed to decrease considerably upon addition of Co and Mn content. The outcome for the tunable magnetic properties and achieved modification of the synthesized nanocrystallites may be chosen for tremendous applications; such as miniaturized memory devices that are based on the energy storage principles and capacitive components. [ABSTRACT FROM AUTHOR]

Nanocrystalline CoCrFeO 4 samples were prepared by Cost effective and low temperature combustion method using different fuels as glycine, urea and polyvinyl alcohol and the effect of temperature on their physical properties has been studied. The thermal study of the precursor gels was done by using Thermogravimetric and Differential thermal analysis (TG-DTA). Occurrence of the cubic spinel phase for the samples was confirmed by the Rietveld analysis of X-ray diffraction (XRD) data. The refinement results also confirm that the cationic distribution over the tetrahedral and octahedral sites in the spinel lattice of samples is partially inverse. The magnetic studies indicate a superparamagnetic behaviour, showing an increase in the blocking temperatures with the particle size in case of all fuels. All the samples showed ferromagnetic behaviour and the nanoparticles prepared by using glycine as a fuel were found to have largest crystallite size and relatively stronger A–O–B interaction compared to others. Magnetization measurements exhibit non-collinear ferrimagnetic structure for the samples. [ABSTRACT FROM AUTHOR]