Iranian Journal of Materials Science and Engineering

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Yellow-colored nitrogen doped TiO2 photocatalyst and a pure TiO2 powder were synthesized via sol-gel method using TiCl4 and urea as raw materials. However, the synthesis procedure for nitrogen doped TiO2 was catalyzed by acid that dialed with controlled precipitation and slow nucleation. According to XRD analysis, the nitrogen doped TiO2 consisted of anatase phase of titania which was a significant achievement regarding its possible photocatalytic applications. The band gaps of nitrogen doped TiO2 and pure TiO2 were estimated from UV-Vis spectroscopy data to be 2.8 and 3.3 ev, respectively. Photocatalytic properties of the nitrogen doped TiO2 nanocatalyst and pure TiO2 were compared for degradation of crystal violet dye in visible light irradiation. In comparison to pure TiO2, nitrogen doped TiO2 showed superior photocatalytic efficiency towards the dye.

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In the following research, Lead magnesium niobate relaxor ferroelectric (PMN-PZT) ceramic powders were synthesized using the combustion method grand urea as the fuel for the first time. The starting materials used were lead nitrate, magnesium acetate, niobium oxide, zirconium nitrate, titanium oxide.

    The raw materials were first mixed using the general formula of (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPb(Zr_0.52Ti_0.48)O₃, with  x=0.3. The synthesized powders were characterized using XRD, SEM and FTIR spectroscopy techniques. The X-ray diffraction patterns revealed that the structure of the prepared samples were tetragonal at 500,600,700 and 800 ^oC. However, the monoclinic phase was detected in the samples calcined at 800 ^oC and the amount of pyrocholore phase also drastically decreased at this temperature. The band gap widths of the samples were measured via UV spectroscopy in the wave number range of 400-4000cm^-1. The results show that by increasing the calcination temperature, the band gap width of the prepared samples decreases. SEM micrographs verify that by rising the calcination temperature, the structure of the prepared samples becomes more homogenous.

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In this work, the effects of co-precipitation temperature and post calcination on the magnetic properties and photocatalytic activities of ZnFe₂O₄ nanoparticles were investigated. The structure, magnetic and optical properties of zinc ferrite nanoparticles were characterized by X-ray diffraction (XRD), vibrating sample magnetometry and UV–Vis spectrophotometry techniques.  The XRD results showed that the coprecipitated as well as calcined nanoparticles are single phase with partially inverse spinel structures. The magnetization and band gap decreased with the increasing of co-precipitation temperature through the increasing of the crystallite size. However, the post calcination at 500 °C was more effective on the decreasing of magnetization and band gap. Furthermore, photocatalytic activity of zinc ferrite nanoparticles was studied by the degradation of methyl orange under UV-light irradiation. Compare with the coprecipitated ZnFe₂O₄ nanoparticles with 5% degradation of methyl orange after 5 h UV-light light radiation, the calcined ZnFe₂O₄ nanoparticles exhibited a better photocatalytic activity with 20% degradation.

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In this research, the dependence of the optical band gap of nano gamma alumina on the OH/Al ratio and concentration of aluminum sulfate is measured through diffuse reflectance spectroscopy (DRS) in the range of 900-1100nm. The samples were prepared via sol-gel method. The results showed that the band gap is pH and concentration-dependent but in a different way. The direct band gap of alumina was determined to be 3.40, 4.37, 3.90, and 3.65 eV for samples prepared at pH 6, 7, 8, and 9, respectively.  A decreasing trend was observed with increasing pH (except for pH6). The lowering of the band gap may be associated with the variations in particles size during synthesis due to the quantum size effect. The values of the band gap increased significantly through increasing concentration from 3.90 to 5.65 eV for 0.1M to 0.3M. The role of concentration in band gap control is remarkably more than pH.

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Indium tin oxide (ITO) nanoparticles were synthesized by green combustion method using indium (In) and tin (Sn) as precursors, and Carica papaya seed extract as novel fuel. This paper highlights effect of tin concentration (5%, 10% and 50%) on microstructural, optical and electrical properties of ITO nanoparticles (NPs). The indium nitrate and tin nitrate solution along with the fuel were heated at 600 °C for 1 h in muffle furnace and obtained powder was calcinated at 650 °C for 3 h to produce ITO NPs. The above properties were investigated using XRD, FTIR, UV-Vis spectroscopy, SEM, TEM and computer controlled impedance analyser. The XRD, SEM and TEM investigations reveals the synthesized NPs were spherical in shape with an increase in average grain size (17.66 to 35 nm) as Sn concentration increases. FTIR investigations confirms the In-O bonding. The optical properties results revealed that the ITO NPs band gap decreased from 3.21 to 2.98 eV with increase in Sn concentration. The ac conductivity of ITO NPs was found to increase with increase in Sn concentration. These synthesised ITO NPs showed the excellent properties for emerging sensor and optical device application.

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This contribution evaluates the influence of Cr doping on the ground state properties of SrTiO3 Perovskite using GGA-PBE approximation. Results of the simulated model infer agreement with the previously published literature. The modification of electronic structure and optical properties due to Cr3+ doping levels in SrTiO3 has been investigated. Structural parameters infer that Cr3+ doping alters the electronic structures of SrTiO3 by shifting the conduction band through lower energies for the Sr and Ti sites. Substituting Ti site by Cr3+ results the energy gap in being eliminated revealing a new electrical case of conducting material for the system. Furthermore, it has been noticed that Cr doping either at Sr or Ti positions could effectively develop the SrTiO3 dielectric constant properties. Consequently, Cr3+ is an effective dopant due to enhancing the optical absorption properties, thus opening up new prospects for optoelectronic applications.