Solution Combustion Synthesis

, Synthesis of nanocrystalline spinel ferrite (MFe 2 O 4 , M = Zn and Mg) by solution combustion method: Influence of fuel to oxidizer ratio, Abstract: Fuel to oxidizer ratio is a critical parameter that determines the properties of nanocrystalline ferrites prepared by solution combustion method. In this study, the influence of fuel to oxidizer ratio on the purity of phase and physical properties of Zinc and Magnesium ferrite nanoparticles prepared by solution combustion method using glycine as fuel is reported. PXRD and FTIR studies on the samples prepared under fuel lean and fuel rich conditions show that there is a gradual variation in the impurity phase as the F/O ratio is varied. Magnetic studies using VSM and Mössbauer spectroscopy show that a reducing environment is created during the combustion process, which influences the magnetic properties of the samples. Mössbauer studies also show that cation redistribution between the tetrahedral and octahedral sites of the as prepared samples also is an important factor which determines the magnetic properties.

Occupation of Fe in ZnO structure X-ray diffraction Mössbauer spectroscopy UV-Vis diffuse reflectance spectroscopy A B S T R A C T A series of Fe-doped ZnO (Zn 1-x Fe x O, x = 0, 0.01, 0.03, 0.05, 0.07 and 0.10) samples were synthesized by solution combustion synthesis method using metal nitrates as oxidizers and glycine as fuel. A spongy network-type microstructure is observed by the SEM micrographs of all the synthesized samples. For Fe concentration lower than 0.05 (x ≤ 0.05), formation of phase-pure wurtzite (hexagonal) structured Zn 1-x Fe x O powder with P6 3 mc space group was confirmed from the X-ray diffraction results. However, for x ≥ 0.07, precipitation of ZnFe 2 O 4 impurity phase was observed. Hence, the solubility limit for Fe in ZnO lattice is about x = 0.05 for the samples synthesized by solution combustion method. Two quadruple doublets observed in the 57 Fe-Mössbauer spectra for each of the samples suggest that paramagnetic Fe 3+ cations occupy two different lattice sites in the ZnO structure; they are the substitutional sites (1) without distortion of the surrounding structure and (2) with distortion due to the defects present in the surrounding structure. In the DRS spectra, an Urbach-like tail was observed in the band gap region, indicating that Fe-doping in the ZnO lattice modifies the electronic structure and enhances the absorption of visible light. Furthermore, the Kubelka-Munk plots suggest the presence of two different local structures validating the Mössbauer results. We studied the photocatalytic degradation of me-thylene blue dye using these Fe doped ZnO samples as catalysts and the studies revealed that presence of Fe could lead to the formation of carbonaceous material on the surface of the solution combustion synthesized Zn 1-x Fe x O samples. Overall, our results demonstrate the structural characteristics of Fe in Fe-doped ZnO samples synthesized by solution combustion method.

Spinels form an interesting class of compounds, finding applications in metal-ion batteries and as catalysts for metal−air batteries and fuel cells. Here, we report a fast, template-free solution combustion method to synthesize nanoscale zinc spinels for applications as cathodes in low-cost aqueous zinc-ion batteries and oxygen reduction reaction (ORR) catalysts. It leads to the formation of phase-pure spinels with near spherical nanoscale morphology. Three spinelsZnCo 2 O 4 (ZCO), ZnMn 2 O 4 (ZMO), and ZnMnCoO 4 (ZMCO)were investigated. ZMO and, for the first time, ZMCO were observed to show reversible Zn (de)insertion involving Mn 4+ /Mn 3+ redox couple with a first discharge capacity of 109.4 mAh/g (i.e., >99% of theoretical capacity). Further, these Zn-based spinels showed appreciable oxygen reduction reaction (ORR) electrocatalytic activity. The ORR activity in alkaline solution was characterized by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) using a rotating disk electrode (RDE) and was observed to be comparable to Pt/C with similar chronoamperometric stability. This enhanced ORR activity can be rooted to the optimal tuning of Co 3+ −O bond strength because of the presence of Mn 3+. This work presents a robust synthesis route to prepare ZnMnCoO 4 spinel acting as an economic cathode material for large-scale Zn-ion batteries for grid storage applications as well as an efficient and stable alternate ORR catalyst in alkaline solution.

Single phase MFeCrO 4 (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO 4 and NiCrFeO 4 samples are 8.374 and 8.325 Å and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm −1 , indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO 4 having a higher value of saturation magnetisation. Mössbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe 3+ cations is higher in NiCrFeO 4 .

A B S T R A C T Aluminium substituted yttrium-iron garnet (Y 3 Al x Fe 5−x O 12 , x = 0, 1, 2, 3, 4 and 5) powders were synthesized by solution combustion route followed by calcination at 1000 °C for 6 h. According to the X-ray diffraction (XRD) results, the as-prepared samples were amorphous. Calcination of the samples at 1000 °C for 6 h results in the formation of phase pure (Ia3 d) garnet structure. The morphology of the samples (for all compositions) were found to be coral-network-like. The Rietveld refinement of the XRD patterns and the Mössbauer spectroscopy confirmed that Y 3+ ions occupy the dodecahedral site, whereas Al 3+ and Fe 3+ ions are distributed in the tetrahedral and octahedral sites of the bcc (Ia3 d) structure of the garnet phase. The Al 3+ ions have a preference to occupy the octahedral site. The lattice parameter decreases with increase in Al-content due to the small size of the Al 3+ cations. For the yttrium-iron-garnet (YIG) sample (x = 0), a saturation magnetization (M S) value of ~ 29 emu/g was obtained, which decreases to ~ 7 emu/g for the sample with x = 2. Further addition of Al makes the garnets paramagnetic. The coral network shape of our garnet samples renders them useful for various applications in catalysis.

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 hyper-fine 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.

Silver is known to be a highly mobile (low soluble) component in Ag doped perovskite mangan ites and hence several non perovskite phases can exist in silver doped manganite perovskites with most syn thetic routes making its synthesis to be problematic. In search of soft synthesis route, the low temperature combustion synthesis and magneto structural studies of polycrystalline La 1 -x Ag y MnO 3 (y ≤ x) ceramic man ganites using glycine as a fuel is reported. The sintered powders were characterized by X Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X ray (EDAX) analysis, Thermo Gravi metric Analysis (TGA) and Vibrating Scanning Magnetometer (VSM) measurements. XRD patterns showed formation of mainly single rhombohedral perovskite phase for the La 0.8 Ag 0.15 MnO 3 sample and an admixture of secondary phases with La 0.8 Ag 0.1 MnO 3 and La 0.8 Ag 0.2 MnO 3 samples. The distinct microstructure and higher magnetic properties observed for La 0.8 Ag 0.15 MnO 3 sample compared to the other samples were dis cussed based on the XRD results.

Crystalline a-Al2O3 was synthesized by the solution combustion of aluminum nitrate and urea in aqueous media. The effect of conditions was further investigated in detail. The XRD analysis shows that the crystalline -Al2O3 was obtained directly by SC method without annealing at high temperature above 1100oC, and the crystalline size can estimate from XRD result. The SEM micrograph shows the morphology of particles. Thermal behavior of a-Al2O3 was evaluated by applying Thermal gravimetric and differential thermal analysis (TG/DTA).

Sunlight is arguably the most promising continuous and cheap alternative sustainable energy source available at almost all living places of the human world. Photovoltaics (PV) is a process of direct conversion of sunlight into electricity and has become a technology of choice for sustainable production of cleaner and safer energy. The solar cell is the main component of any PV technology and transparent conducting oxides (TCO) comprising wide band gap semiconductors are an essential component of every PV technology. In this research, transparent conducting thin films were prepared by solution combustion synthesis of metal oxide nitrates wherein the use of indium is substituted or reduced. Individual 0.5 M indium, gallium and zinc oxide source solutions were mixed in ratios of 1:9 and 9:1 to obtain precursor solutions. Indium-rich IZO (A1), zinc-rich IZO (B1), gallium-rich GZO (C1) and zinc-rich GZO (D1) thin films were prepared through spin coating deposition. In the case of A1 and ...

Nanosized powders of Gd substituted Mg-Mn ferrites synthesized by solution combustion method using high purity metal nitrates are presented. These powders were calcined, compacted and sintered at 1250°C. The powders were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The effect of Gd substitution on phase formation, microstructure and bulk density was also studied. Gd 2 O 3 facilitates the formation of a secondary phase on the grain boundary which suppresses abnormal grain growth. The bulk density was found to decrease from 4.26 to 3.38 g/cm 3 with an increase of Gd substitution, but the electrical resistivity was increased. Ferrite with a low dielectric constant in the range of 6-12 was observed and there was no maximum dielectric loss in the frequency range measured to 1 GHz. A decrease in saturation magnetization was also observed by a small fraction of Gd substitution. Correlation between magnetic properties and physical properties were discussed.

Sunlight is arguably the most promising continuous and cheap alternative sustainable energy source available at almost all living places of the human world. Photovoltaics (PV) is a process of direct conversion of sunlight into electricity and has become a technology of choice for sustainable production of cleaner and safer energy. The solar cell is the main component of any PV technology and transparent conducting oxides (TCO) comprising wide band gap semiconductors are an essential component of every PV technology. In this research, transparent conducting thin films were prepared by solution combustion synthesis of metal oxide nitrates wherein the use of indium is substituted or reduced. Individual 0.5 M indium, gallium and zinc oxide source solutions were mixed in ratios of 1:9 and 9:1 to obtain precursor solutions. Indium-rich IZO (A1), zinc-rich IZO (B1), gallium-rich GZO (C1) and zinc-rich GZO (D1) thin films were prepared through spin coating deposition. In the case of A1 and B1 thin films, electrical resistivity obtained was 3.4 × 10−3 Ω-cm and 7.9 × 10−3 Ω-cm, respectively. While C1 films remained insulating, D1 films showed an electrical resistivity of 1.3 × 10−2 Ω-cm. The optical transmittance remained more than 80% in visible for all films. Films with necessary transparent conducting properties were applied in an all solution-processed solar cell device and then characterized. The efficiency of 1.66%, 2.17%, and 0.77% was obtained for A1, B1, and D1 TCOs, respectively, while 6.88% was obtained using commercial fluorine doped SnO2: (FTO) TCO. The results are encouraging for the preparation of indium-free TCOs towards solution-processed thin-film photovoltaic devices. It is also observed that better filtration of precursor solutions and improving surface roughness would further reduce sheet resistance and improve solar cell efficiency.

AlN powders were prepared by combining sodium fluoride-assisted solution combustion with carbothermal reduction-nitridation. The effects of sodium fluoride on the nitridation reactivity, specific surface areas and morphology of the synthesized AlN powders were investigated in detail. The morphology of the AlN products changed from highly fluffy and porous networks into regular and hexagonal thin flakes, and the specific surface area decreased with the sodium fluoride content. No hard agglomeration could be found in decarburized AlN powders. The phase-pure AlN has been observed in all products calcined above 1300 1C, and no sodium was detected in the AlN powders by the X-ray fluorescence spectrometry.

Sunlight is arguably the most promising continuous and cheap alternative sustainable energy source available at almost all living places of the human world. Photovoltaics (PV) is a process of direct conversion of sunlight into electricity and has become a technology of choice for sustainable production of cleaner and safer energy. The solar cell is the main component of any PV technology and transparent conducting oxides (TCO) comprising wide band gap semiconductors are an essential component of every PV technology. In this research, transparent conducting thin films were prepared by solution combustion synthesis of metal oxide nitrates wherein the use of indium is substituted or reduced. Individual 0.5 M indium, gallium and zinc oxide source solutions were mixed in ratios of 1:9 and 9:1 to obtain precursor solutions. Indium-rich IZO (A1), zinc-rich IZO (B1), gallium-rich GZO (C1) and zinc-rich GZO (D1) thin films were prepared through spin coating deposition. In the case of A1 and ...

Single phase MFeCrO 4 (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO 4 and NiCrFeO 4 samples are 8.374 and 8.325 Å and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm −1 , indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO 4 having a higher value of saturation magnetisation. Mössbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe 3+ cations is higher in NiCrFeO 4 .

Sunlight is arguably the most promising continuous and cheap alternative sustainable energy source available at almost all living places of the human world. Photovoltaics (PV) is a process of direct conversion of sunlight into electricity and has become a technology of choice for sustainable production of cleaner and safer energy. The solar cell is the main component of any PV technology and transparent conducting oxides (TCO) comprising wide band gap semiconductors are an essential component of every PV technology. In this research, transparent conducting thin films were prepared by solution combustion synthesis of metal oxide nitrates wherein the use of indium is substituted or reduced. Individual 0.5 M indium, gallium and zinc oxide source solutions were mixed in ratios of 1:9 and 9:1 to obtain precursor solutions. Indium-rich IZO (A1), zinc-rich IZO (B1), gallium-rich GZO (C1) and zinc-rich GZO (D1) thin films were prepared through spin coating deposition. In the case of A1 and ...

Nanosized powders of Gd substituted Mg-Mn ferrites synthesized by solution combustion method using high purity metal nitrates are presented. These powders were calcined, compacted and sintered at 1250°C. The powders were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The effect of Gd substitution on phase formation, microstructure and bulk density was also studied. Gd 2 O 3 facilitates the formation of a secondary phase on the grain boundary which suppresses abnormal grain growth. The bulk density was found to decrease from 4.26 to 3.38 g/cm 3 with an increase of Gd substitution, but the electrical resistivity was increased. Ferrite with a low dielectric constant in the range of 6-12 was observed and there was no maximum dielectric loss in the frequency range measured to 1 GHz. A decrease in saturation magnetization was also observed by a small fraction of Gd substitution. Correlation between magnetic properties and physical properties were discussed.

Nanosized powders of Gd substituted Mg-Mn ferrites synthesized by solution combustion method using high purity metal nitrates are presented. These powders were calcined, compacted and sintered at 1250 degrees C. The powders were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The effect of Gd substitution on phase formation, microstructure and bulk density was also studied. Gd2O3 facilitates the formation of a secondary phase on the grain boundary which suppresses abnormal grain growth. The bulk density was found to decrease from 426 to 3.38 g/cm(3) with an increase of Gd substitution, but the electrical resistivity was increased. Ferrite with a low dielectric constant in the range of 6-12 was observed and there was no maximum dielectric loss in the frequency range measured to 1 GHz. A decrease in saturation magnetization was also observed by a small fraction of Gd substitution. Correlation between magnetic properties and physical properties were discussed. (C) 2015 Elsevier B.V. All rights reserved.

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