Synthesis, structural and ferromagnetic properties of La1-xKxMnO3 (0.0 <= x <= 0.25) phases by solution combustion method

We describe the solution combustion synthesis and characterization of La1-xKxMnO3 (0.0 <= x <= 0.25) perovskite phases, which is a low temperature initiated, rapid route to prepare metal oxides. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800 degrees C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent LaMnO3 compound crystallizes in the orthorhombic structure (space group Pbnm, No. 62). Potassium substituted compounds were crystallized with rhombohedral symmetry (space group R-3c, No. 167). The ratio of the Mn3+/Mn4+ was determined by the iodometric titration. The Fourier transform infrared spectrum (FTIR) shows two absorption bands for Mn-O stretching vibration (v, mode), Mn-O-Mn deformation vibration (v(b) mode) around 600 cm(-1) and 400 cm(-1) for the compositions, x = 0.0, 0.05 and 0-10. Four-probe electrical resistivity measurements reveal a composition controlled metal to insulator transition (TM-1), the maximum TM-1 was observed for the composition La0.85K0.15MnO3 at 287 K. Room temperature vibrating sample magnetometer data indicate that for the composition up to x = 0-10, the compounds are paramagnetic whereas composition with x = 0.15, 0.20 and 0.25 show magnetic moments of 27, 29 and 30 emu/g, respectively

Synthesis and characterization of cation-doped BiFeO₃ materials for photocatalytic applications

131-139A sol-gel method was applied to synthesize Bi1-xMxFeO3 (M = Mg, Al, Y) ceramic materials. Subsequently, these materials were structurally characterized by applying Rietveld refinement techniques. The magnetic properties of the synthesized materials were determined by SQUID measurements and their optical properties (band-gap) were determined by applying diffused reflectance (DR) techniques. The low band-gap nature of these materials enabled to them exhibit photocatalytic activity and accordingly 2% Y doped BiFeO3 samples exhibited higher photocatalytic effect (18% compared to 14% for undoped). Under identical conditions, TiO2 standard exhibited only 7% degradation indicating superior properties of cation-doped bismuth ferrites

Rapid Synthesis of Ferromagnetic La1−xNaxMnO3La_{1-x}Na_xMnO_3 (0.00≤x≤0.25)(0.00\leq x\leq 0.25) by the Solution Combustion Method

Rapid synthesis of sodium-substituted lanthanum manganite phases is reported by the solution combustion method using oxalyl dihydrazide (ODH), as fuel. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800°C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder X-ray diffraction data. Parent $LaMnO_3$ compound crystallizes in the orthorhombic structure (space group Pbnm No. 62). Sodium-substituted compounds crystallize with rhombohedral symmetry (space group R-3c, No.167). On increasing the sodium content, unit cell volume decreases and Mn–O–Mn bond angle increases. The fourier transform infrared spectrum shows two absorption bands around 600 and $400 cm^{−1}$ for the compositions x=0.0, 0.05, and 0.10. $Mn^{3+}/Mn^{4+}$ ratio was determined by iodometric titration. Electrical resistivity measurements reveal a composition-controlled metal to insulator transition $(T_{M-I})$, the maximum $T_{M-I}$ was observed for the composition $La_{0.85}Na_{0.15}MnO_3$ at 285 K. Increase in magnetic moment is observed with increase in crystallite size. Room temperature vibrating sample magnetometer data indicate that for the composition up to x=0.10, the compounds are paramagnetic whereas composition with x=0.15, 0.20, and 0.25 show magnetic moments 34, 39, and 33 emu/g, respectively

Kinetics of oxidative decarboxylation and deamination of L-glutamine by diperiodatonickelate(IV) in aqueous alkaline medium

1639-1644The kinetics of oxidation of L-glutamine by diperiodatonickelate (IV) (DP) in aqueous alkaline medium at a constant ionic strength of 0.5 mol dm-3 has been studied spectrophotometricall y. The reaction is first order in [DPN] and is an apparent less than unit order, each in [L-glutamine] and [alkali] under the experimental conditions. However, the order in [L -glutamine] and [alkali] changes from first order to zero order as the concentrations change from lower to higher concentrations. Addition of periodate has no effect of the rate of reaction. Effect of added products, ionic strength and dielectric constant of the reaction medium have been investigated . A mechanism involving the deprotonated diperiodatonickelate(IV) as the reactive species of the oxidant has been proposed. The reaction constants involved in the different steps of mechanism are evaluated and thermodynamic quantities are also calculated

Kinetic and mechanistic study of oxidative degradation of isonicotinate ion by diperiodatonickelate(IV) in aqueous alkaline medium

587-592The kinetics of oxidation of isonicotinate ion by alkaline diperiodatonickelate(IV) has been studied spectrophotometrically. The reaction is first order with respect to [DPN] and is apparently less than unit order each in [isonicotinate ion] and [alkali] under the experimental conditions. However, the order in Lisonicotinate ion] and [alkali] changes from first order to zero order as their concentrations increase. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Addition of periodate has no effect on the reaction rate. A mechanism involving the deprotonated diperiodatonickelate(IV) (DPN) as the reactive oxidant species has been proposed. There is a good agreement between the observed and calculated rate constants under varying experimental conditions. The activation parameters with respect to the slow step of scheme have been discussed

Rapid Synthesis of Ferromagnetic La1−xNaxMnO3La_{1-x}Na_xMnO_3 (0.00≤x≤0.25)(0.00\leq x\leq 0.25) by the Solution Combustion Method

Rapid synthesis of sodium-substituted lanthanum manganite phases is reported by the solution combustion method using oxalyl dihydrazide (ODH), as fuel. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800°C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder X-ray diffraction data. Parent $LaMnO_3$ compound crystallizes in the orthorhombic structure (space group Pbnm No. 62). Sodium-substituted compounds crystallize with rhombohedral symmetry (space group R-3c, No.167). On increasing the sodium content, unit cell volume decreases and Mn–O–Mn bond angle increases. The fourier transform infrared spectrum shows two absorption bands around 600 and $400 cm^{−1}$ for the compositions x=0.0, 0.05, and 0.10. $Mn^{3+}/Mn^{4+}$ ratio was determined by iodometric titration. Electrical resistivity measurements reveal a composition-controlled metal to insulator transition $(T_{M-I})$, the maximum $T_{M-I}$ was observed for the composition $La_{0.85}Na_{0.15}MnO_3$ at 285 K. Increase in magnetic moment is observed with increase in crystallite size. Room temperature vibrating sample magnetometer data indicate that for the composition up to x=0.10, the compounds are paramagnetic whereas composition with x=0.15, 0.20, and 0.25 show magnetic moments 34, 39, and 33 emu/g, respectively

Solution-combustion synthesis of Bi1−xLnxO1.5Bi_{1-x}Ln_xO_{1.5} (Ln = Y and La–Yb) oxide ion conductors

Cubic fluorite related $Bi_{1-x}Ln_xO_{1.5}$ (Ln = Y and La–Yb) phases are synthesized by solutioncombustion method using glycine as the fuel. The cubic fluorite phase is stabilized with 25 mole% of rare earth cations. The lattice parameter of cubic phase increases linearly with size of the lanthanide ion. The synthesized powders are nano-metric in size and exhibit excellent compactability and reach 98% densification even on short period of sintering. The oxides with relatively larger cations Nd, Sm, Eu, Pr and Gd with 25 mole% composition transform to rhombohedral structure while others retain cubic upon sintering. All the phases show high oxide–ion conductivity and the values obtained are in good agreement with the reported values

Synthesis, characterization, redox and photocatalytic properties of Ce1−xPdxVO4Ce_{1-x}Pd_{x}V_{O4} (0 ≤x≤\leq x \leq 0.1)

Zircon-type CeVO4 and Ce1-xPdxVO4 (0.02 <= x <= 0.1) were synthesized by a single step solution combustion method. The materials were characterized by powder X-ray diffraction, magnetic measurement and temperature-programmed reduction (TPR) with H-2. The redox properties of CeVO4 and Ce0.98Pd0.02VO4 have been investigated by temperature-programmed reduction. The gas-phase and liquid-phase catalytic properties of CeVO4 and Ce0.98Pd0.02VO4 were investigated. Ce0.98Pd0.02VO4 shows better catalytic activity than CeVO4 towards CO oxidation by O-2, NO reduction by CO and the photocatalytic degradation of various dyes. This higher catalytic activity of Ce0.98Pd0.02VO4 can be attributed to the lattice labile oxygen and high surface area compared to that of CeVO4

Synthesis, characterization, redox and photocatalytic properties of Ce1-xPdxVO4 (0 <= x <= 0.1)

Zircon-type CeVO4 and Ce1−xPdxVO4 (0.02 ≤ x ≤ 0.1) were synthesized by a single step solution combustion method. The materials were characterized by powder X-ray diffraction, magnetic measurement and temperature-programmed reduction (TPR) with H2. The redox properties of CeVO4 and Ce0.98Pd0.02VO4 have been investigated by temperature-programmed reduction. The gas-phase and liquid-phase catalytic properties of CeVO4 and Ce0.98Pd0.02VO4 were investigated. Ce0.98Pd0.02VO4 shows better catalytic activity than CeVO4 towards CO oxidation by O2, NO reduction by CO and the photocatalytic degradation of various dyes. This higher catalytic activity of Ce0.98Pd0.02VO4 can be attributed to the lattice labile oxygen and high surface area compared to that of CeVO4

Synthesis, structure and oxygen-storage capacity of Pr<SUB>1-x</SUB>Zr<SUB>x</SUB>O<SUB>2-&#948;</SUB> and Pr<SUB>1-x-y</SUB>Pd<SUB>y</SUB>Zr<SUB>x</SUB>O<SUB>2-&#948;</SUB>

Nanocrystalline Pr1-xZrxO2-&#948; (0 &#8804; x &#8804; 1) and Pr1-x-yPdyZrxO2-&#948; (x = 0.50, y = 0.02) solid solutions have been synthesized by a single step solution combustion method. The whole range of solid solution compositions crystallize in cubic fluorite structure. The lattice parameter 'a' linearly varied up to x = 1.0. Oxygen-storage capacity (OSC) and redox properties of Pr1-xZrxO2-&#948; (0.0 &#8804; x &#8804; 0.8) solid solutions have been investigated by temperature-programmed reduction (TPR) and are compared with those of Ce1-xZrxO2. Pr1-xZrxO2-&#948; exhibited H2 uptake and CO oxidation at a lower temperature than Ce1-xZrxO2. Small amount of Pd ion (y = 0.02) substitution was found to bring down the temperature of oxygen release-storage significantly