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Papers by Tahere Ghorbani-Moghadam

Journal of Alloys and Compounds

Ceramics International, 2021

Abstract In this research, photocatalytic properties of La0.7Sr1.3CoO4 Ruddlesden-Popper oxide ha... more Abstract In this research, photocatalytic properties of La0.7Sr1.3CoO4 Ruddlesden-Popper oxide have been investigated on methyl orange (MO) dye degradation under UV irradiation for the first time. Nanopowders of La0.7Sr1.3CoO4 were synthesized by a modified sol-gel method. The synthesized powders were characterized using XRD analysis, FE-SEM and TEM imaging techniques, Raman and UV–Vis spectroscopy. The XRD pattern revealed that the synthesized powders crystalize in tetragonal structure with I4/mmm space group and the optical band gap was evaluated about 2.5 eV, using tauc equation. Photo-degradation of 20 mL of MO solution was studied for different amounts of La0.7Sr1.3CoO4 (0.025, 0.050 and 0.1 g), as the photocatalysts. Moreover, the effect of different amounts of hydrogen peroxide (H2O2), as an electron acceptor, on the catalytic reaction was also investigated. Our results showed that MO degradation efficiency over the optimal amount of La0.7Sr1.3CoO4 was about 94% under UV irradiation after 75 min. This efficiency and the rate of MO degradation was found to increase with the presence of H2O2, as an oxidant. These results suggest that La0.7Sr1.3CoO4 nanopowder can be considered as a good and promising photocatalyst for dye degradation.

a b s t r a c t Calcium manganese oxide CaMnO3δ (δ0.02) nanopowders were synthesized by two diffe... more a b s t r a c t Calcium manganese oxide CaMnO3δ (δ0.02) nanopowders were synthesized by two different methods; sol–gel and solid-state reaction. X-ray diffraction patterns indicated that both types of the prepared powders have orthorhombic symmetry structures at room temperature. Further characterizations of the samples were preformed employing SEM and TEM techniques. At low magnetic fields, the phase transition temperature from antiferromagnetic to paramagnetic was found to be slightly higher in the sintered O-ring shape specimens made from powders synthesized by sol–gel method. This result can be described in relation to Mn3þ–O–Mn4þ double-exchange interaction and also electron hopping mechanism which occur more in these specimens than those made from solid-state reaction powders. The frequency dependence of Néel temperature and the shape of the hysteresis loops, observed in both types of the prepared ceramics specimens, can be attributed to the reduction of relaxation time which ...

Journal of Alloys and Compounds, 2022

Journal of Electronic Materials, 2020

In this study, Ruddlesden-Popper La 0.9 Sr 1.1 Co 1Àx Mo x O 4 (x £ 0.1) powders were successfull... more In this study, Ruddlesden-Popper La 0.9 Sr 1.1 Co 1Àx Mo x O 4 (x £ 0.1) powders were successfully synthesized using a modified sol-gel method. The structural analysis revealed that all samples had a tetragonal phase at room temperature. The electrical conductivity measurements showed that all samples had semiconducting behavior in the range of room temperature to 850°C. Moreover, it was found that the electrical conductivity of the ceramics was enhanced with the increase of Mo doping, at temperatures higher than 300°C up to 850°C. This enhancement of the electrical conductivity can be due to Co 3+-O-Mo 5+-O-Co 2+ double-exchange interaction. The EIS measurements of the symmetrical cells were carried out for x = 0, 0.03 and 0.1 samples at 650°C, 750°C and 850°C. The obtained area specific resistance (ASR) values of La 0.9 Sr 1.1 Co 1Àx Mo x O 4 on ceria-gadolinium oxide (CGO) electrolyte at 850°C were 0.36 X cm 2 , 0.35 X cm 2 and 1 X cm 2 for samples x = 0, 0.03 and 0.1, respectively. These results indicate that the electrical conductivity of pure sample (La 0.9 Sr 1.1 CoO 4) has been enhanced by Mo substitution in Co ion sites, but limits the oxygen ion transport.

$Research paper thumbnail of Cobalt spin states investigation of Ruddlesden-Popper La2−xSrxCoO4, using X-ray diffraction and infrared spectroscopy$

Journal of Magnetism and Magnetic Materials, 2018

Ruddlesden-Popper (RP) La 2−x Sr x CoO 4 (x = 0.7, 0.9, 1.1, 1.3) were synthesized by a modified ... more Ruddlesden-Popper (RP) La 2−x Sr x CoO 4 (x = 0.7, 0.9, 1.1, 1.3) were synthesized by a modified sol-gel route. The synthesized samples were characterized by XRD, FE-SEM technique, iodometric titration, FT-FIR spectroscopy and VSM analysis. The variation of CoO bond length obtained from Rietveld refinements and the related peak shifts in the FT-FIR spectra showed that Co 3+ has both LS and IS spin states. It is found that the population of Co 3+ in the LS state decreases and IS state increases with increasing Sr concentration. Jahn-Teller effect was identified in the FT-FIR absorption bands, corresponding to the vibration modes of Co bonds with the apical and equatorial oxygen atoms. The ferromagnetic characteristic of La 0.7 Sr 1.3 CoO 4 , obtained by VSM, revealed the increase of Co 3+ IS population by Sr doping, in agreement with XRD and FT-FIR results. The shift and split of the IR absorption bands with the change in the structural parameters are proposed to be an applicable tool to probe the spin states and Jahn-Teller effect in La 2−x Sr x CoO 4 compounds.

Journal of Magnetism and Magnetic Materials, 2014

Calcium manganese oxide CaMnO 3 À δ (δ¼ 0.02) nanopowders were synthesized by two different metho... more Calcium manganese oxide CaMnO 3 À δ (δ¼ 0.02) nanopowders were synthesized by two different methods; sol-gel and solid-state reaction. X-ray diffraction patterns indicated that both types of the prepared powders have orthorhombic symmetry structures at room temperature. Further characterizations of the samples were preformed employing SEM and TEM techniques. At low magnetic fields, the phase transition temperature from antiferromagnetic to paramagnetic was found to be slightly higher in the sintered O-ring shape specimens made from powders synthesized by sol-gel method. This result can be described in relation to Mn 3 þ-O-Mn 4 þ double-exchange interaction and also electron hopping mechanism which occur more in these specimens than those made from solid-state reaction powders. The frequency dependence of Néel temperature and the shape of the hysteresis loops, observed in both types of the prepared ceramics specimens, can be attributed to the reduction of relaxation time which occurs with increasing the frequency.

Materials Science and Engineering: B

This paper describes the synthesis of CaMnO3 ceramic nanopowders by sol-gel procedure. Metal acet... more This paper describes the synthesis of CaMnO3 ceramic nanopowders by sol-gel procedure. Metal acetate precursors were used, as starting materials. Single phase perovskite structure of CaMnO3 was formed, at calcination temperature 800°C for two hours. The samples were characterized using XRD, UV, TEM and SEM methods. The electrical resistivity and energy band gap were also measured.