Cobalt substituted La2CuO4/LaCoO3 perovskite nanocomposites were prepared using a microwave combustion method.

John Kennedy L

Physics

School of Advanced Sciences

Chennai Campus

Sukumar M

Vijaya J.J

Al-Najar B

Bououdina M.

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

New Journal of Chemistry

Ca2+ substituted La2CuO4 (LCC) perovskite nanostructures have been prepared by microwave combustion. X-ray diffraction analysis indicates that the undoped La2CuO4 (LCC0) crystallizes within a single perovskite-type phase with an orthorhombic crystal structure. For smaller Ca2+ doping of 0.1 (LCC1), a minor impurity was observed, while for concentrations 0.2 (LCC2) and 0.3 (LCC3), orthorhombic-to-tetragonal phase transformation occurs. In contrast, the tetragonal phase disappears at 0.4 and 0.5 (LCC4 and LCC5) as confirmed by XRD and Rietveld refinements. The orthorhombic and tetragonal perovskite phases have an average crystallite size in range 34.2–54.3 nm and 39.8–39.4 nm, respectively. Fourier transform infrared spectroscopy study established the characteristic absorption bands of La2CuO4 perovskite orthorhombic structure; the correlated bands are observed at 683 cm−1 for La-O and 516 cm−1 for Cu-O stretching modes. The optical band gap as determined by diffuse reflectance spectroscopy (DRS) increases then decreases with increasing Ca2+ content due to the quantum confinement effect. The surface morphology observations using scanning electron microscopy display nano-sized pores and pore walls are fused grain boundaries. Magnetization-field curves exhibit a ferro-/paramagnetic behavior for undoped La2CuO4 while Ca-doped system has only a paramagnetic behavior due to the exchange of A and B sites within La2CuO4 host lattice. © 2019 Elsevier Ltd

Vacuum

Structural, optical, and magnetic properties of Ca2+ doped La2CuO4 perovskite nanoparticles

Journal of Nanoscience and Nanotechnology

Catalytic Conversion of Methanol to Formaldehyde Over La2CuO4 Nanoparticles

Barium doped La2CuO4 perovskite nanoparticles were synthesized via microwave assisted combustion method. The effects of Ba2+ doping on structural, optical, magnetic and catalytic activity of La2CuO4 have been studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and vibrating sample magnetometer (VSM) techniques. The XRD patterns of pure La2CuO4 and La1.9Ba0.1CuO4 confirmed the formation of perovskite structure without impurities. However, with increasing Ba2+ content in the range 0.2–0.5, phase transformation from orthorhombic to tetragonal structure, occurred. The average crystallite size of orthorhombic and tetragonal phases were in the range 45.2–52.2 nm and 0.5–41 nm, respectively. The appearance of FT-IR bands at around 685 and 517 cm−1 were correlated to the La-O and Cu-O stretching modes of orthorhombic La2CuO4 phase. The direct band gap estimated using Kubelka–Munk (K–M) method decreased with the increase in Ba2+ content (1.88–1.64 eV), due to the formation of sub-bands in the energy band gap. Magnetic measurements of doped La2CuO4 samples showed either para- or ferro-/para- magnetic behaviour at room temperature. The catalytic activity (oxidation) tests carried out in a batch reactor operating under atmospheric conditions indicated that the prepared catalysts, in particular (La1.7Ba0.3CuO4), showed excellent catalytic activity. © 2018 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Structural, magnetic and catalytic properties of La2-Ba CuO4 (0 ≤ x ≤ 0.5) perovskite nanoparticles

Strontium doped lanthanum cuprate perovskite-type nanostructures were synthesized by facile microwave assisted combustion method. The structural, optical, morphological, and magnetic properties were studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), photoluminescence (PL) and vibrating sample magnetometer (VSM) techniques.The XRD patterns of pure La2CuO4 (LC) and La1.9Sr0.1CuO4 confirmed the formation of perovskite structure without impurities. However with the increase in Sr2+ content from (x = 0.2–0.5), phase transformation from orthorhombic to tetragonal structure, occurred. The average crystallite size of orthorhombic and tetragonal phases were in the range 39.6–47.4 nm and 22.3–88.0 nm, respectively. The presence of tensile strain in Sr2+ doped LC (LSC) was determined from Williamson–Hall (W–H) analysis. The appearance of FT-IR bands at around 688 and 521 cm-1 were correlated to the La-O and Cu-O stretching modes of orthorhombic La2CuO4 phase. The direct band gap estimated using Kubelka–Munk (K–M) method increased with increasing Sr2+ content (1.88–2.03 eV), due to quantum confinement. For LC and LSC, PL spectra showed emission bands in UV and visible regions, due to the defect centers acting as trap levels. The LSC system showed the formation of nanosized crystallized grains with pores and pore-walls due to fused grains. Magnetization–Field (M−H) hysteresis curves revealed the appearance of ferro-/para- magnetic behavior at room temperature. © 2018 Elsevier B.V.

Journal of Magnetism and Magnetic Materials

Facile microwave assisted combustion synthesis, structural, optical and magnetic properties of La2−Sr CuO4 (0 ≤ x ≤ 0.5) perovskite nanostructures

Zn1-xMnxAl2O4 (0 ≤ x ≤ 0.5) spinel nanostructures were synthesized by urea assisted microwave combustion method. Structural, vibrational, morphological, optical and magnetic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM) respectively. The XRD studies showed that the samples have pure cubic spinel phase, which is further validated by Rietveld refinement. The average crystallite size is of the nanoparticles estimated using Debey-Scherrer's method was found to be in the range of 14-17 nm. The lattice parameter is increased from 8.089 to 8.160 Å with increasing in Mn2+ content. The William-Hall (W-H) analysis was used to study the effects of lattice strain over the crystallite size. Increase in lattice parameter and increase in porosity were observed on increasing Mn2+ concentration FTIR spectra showed the vibrational stretching frequencies corresponding to the zinc aluminate spinels. The morphology of the samples depicted the formation of well developed nano-sized clusters with homogeneous well crystallized grains without any agglomerations. The optical band gap value of undoped zinc aluminate nanostructure is higher than the reported bulk zinc aluminate. The direct band gap estimated using Kubelka-Munk method decreased with increasing Mn2+ content (5.05-3.49 eV), due to the formation of sub bands in the energy gap. The photoluminescence characteristics of undoped and Mn2+ doped zinc aluminates are suggestive of defect controlled process and had an effect on the luminescence. Magnetic measurements revealed that the undoped ZnAl2O4 has diamagnetic behavior while the Mn2+ doped ZnAl2O4 system has superparamagnetic behavior. © 2014 Elsevier B.V. All rights reserved.

Journal of Molecular Structure

Structural, optical and magnetic properties of Zn1−xMnxAl2O4 (0⩽x⩽0.5) spinel nanostructures by one-pot microwave combustion technique

Zn1-xNixAl2O4 (0 ≤ x ≤ 0.5) spinel nanostructures were synthesized by microwave combustion technique. Structural, vibrational, optical, morphological and magnetic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance (DRS) and photoluminescence (PL) spectroscopy, high resolution scanning electron microscopy (HR-SEM), and vibrating sample magnetometry (VSM), respectively. The XRD pattern confirmed the formation of a single phase cubic spinel structure of ZnAl2O4 (gahnite), except for higher dopant concentrations for which a secondary phase was observed and validated by Rietveld refinement analysis. Different concentration levels of Ni2+ was used as the dopant in the zinc aluminate matrix. Decrease in lattice parameter and increase in porosity were observed on increasing Ni3+ concentration. The average crystallite size of the nanoparticles estimated using Debey-Scherrer's method was found to be in the range of 8.89-13.84 nm. The William-Hall (W-H) analysis was used to study the effects of lattice strain over the crystallite size. FT-IR spectra showed the vibrational stretching frequencies corresponding to the zinc aluminate spinels. The optical band gap value of undoped zinc aluminate nanostructure is higher than the reported bulk zinc aluminate. The direct band gap estimated using the Kubelka-Munk method decreased with increasing Ni2+ content (5.05-3.98 eV), due to the formation of subbands in the energy gap. The HR-SEM images depict the formation of well developed nano-sized clusters with homogeneous well crystallized grains without any agglomerations. The PL characteristics of undoped and Ni2+ doped zinc aluminates are suggestive of defect controlled process. Magnetic measurements revealed that the undoped ZnAl2O4 has diamagnetic behavior while the Ni2+ doped ZnAl2O4 system has superparamagnetic behavior, despite NiO impurities. © 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Journal	Data powered by TypesetNew Journal of Chemistry
Publisher	Data powered by TypesetRoyal Society of Chemistry (RSC)
ISSN	1144-0546
Open Access	0