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    The influence of thermal processing on microstructure of sol-gel-derived SrSnO3 thin films
    (Springer, 2017) Gül, Esra; Stanulis, Andrius; Barushka, Y.; Garskaite, Edita; Ramanauskas, Rimantas; Morkan, Ayşe Uztetik
    Polycrystalline SrSnO3 thin films were fabricated using the aqueous sol-gel process and deposited on the single crystal sapphire (R-Al2O3 and C-Al2O3) and Si substrates by spin coating technique. Two different processing of thermal treatment was explored to produce SrSnO3 thin films of different porosity. The XRD analysis showed that polycrystalline films with preferential growth of SrSnO3 (200) plane were obtained on C-Al2O3 substrates, while films deposited on R-Al2O3 demonstrated a random polycrystalline growth. FE-SEM analysis revealed that the higher porosity of SrSnO3 films can be achieved by introducing additional thermal treatment step during the deposition procedure. The UV-Vis reflectance spectroscopy was used to study the effect of porosity on optical properties of the films.
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    Structural, morphological, and magnetic characterization of bulk and thin films Y3Al5-xFexO12 (YAIG): from the perspective of aqueous sol-gel processing
    (Taylor & Francis Inc, 2017) Opuchovic, Olga; Cülünlü, Serdar; Morkan, Ayşe Uztetik; Morkan, İzzet Amour; Niznansky, Daniel
    An aqueous sol-gel method was used for the preparation of bulk Y3Al5-xFexO12 (yttrium aluminum-iron garnet, YAIG) with the composition of x=0.0, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0 and thin films with the composition of x=0, 3.0, 4.0, 5.0. The dip-coating technique was used for the preparation of Y3Al5-xFexO12 films on a silicon (Si) substrate. The phase composition and surface morphology of both bulk and coatings were determined and compared. The synthesized powder samples were investigated by X-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy, and Mossbauer spectroscopy. The data provide evidence that some sol-gel-derived powder specimens consist of magnetically ordered component, while others show paramagnetic behavior depending on the composition of the product. It was also shown that sol-gel processing route could be successfully used for the preparation of mixed-metal YAIG thin films.
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    Synthesis, crystal structure, spectroscopic investigations, thermal behavior and DFT calculations of pentacarbonyl(2-methylpyrazine)chromium(0)
    (Pergamon-Elsevier Science Ltd, 2012) Morkan, İzzet Amour; Çelik, Derya; Morkan, Ayşe Uztetik; Güven, Kutalmış
    Pentacarbonyl(2-methylpyrazine)chromium(0) [Cr(CO)(5)(2mpyz)], complex was isolated from its n-hexane solution as orange plate-like crystals which were characterized by IR, NMR spectroscopies and X-ray crystallography. The crystallographic results show that the complex was crystallized in the monoclinic system with the unit cell parameters of a = 7.176 (5), b = 12.045 (3), c = 14.461 (3)angstrom, beta=90.44 (3)degrees and space group 2/M. The single crystal structure of the complex shows the bonding of chromium metal to 2-methylpyrazine through the less sterically hindered nitrogen-4 lone pair. The pyrazine ring plane makes an angle of 179.58 degrees (19) with CO-Cr-N bond axis. The four carbonyl groups are slightly bent away from pyrazine with the angle of 91.28 degrees (17) for C-s-Cr-N1 bond axis. The DFT calculations run out using the Gaussian 03 PC program show good agreement with the experimental results. The thermal properties of the complex were also investigated by differential thermal analysis and thermogravimetry techniques. (C) 2012 Elsevier B.V. All rights reserved.
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    Synthesis, crystal structure, thermal behavior and IR characterization of pentacarbonyl(4-methylpyridine)chromium(0) complex
    (Springer/Plenum Publishers, 2008) Morkan, İzzet Amour; Morkan, Ayşe Uztetik; Tuç, Çiğdem; Kendi, Engin
    Pentacarbonyl(4-methylpyridine)chromium(0) complex was isolated from n-hexane solution as yellow plate-like crystals and characterized by using X-ray crystallography. It crystallizes in the orthorhombic system with the space group Cmcm and Z = 4. The unit cell parameters are a = 11.737(1) angstrom, b = 12.857(2) angstrom, c = 8.465(1) angstrom. The single crystal X-ray structure of the complex shows that the coordination sphere around the chromium central atom is slightly distorted octahedron, involving the 4-methylpyridine (4-mp), ligand as a monodentate N-donor ligand and five carbonyl groups. The four equatorial CO groups in the complex, with the Cr-C2 distance of 1.886 angstrom, are slightly bent away from the 4-methylpyridine ligand with the N-Cr-C2 angle of 91.69. The pyridine ring plane makes an angle of 135.17 with the Cr-N-CO bond axis. The thermal analysis (differential thermal analysis and thermal gravimetry) and IR spectra of the complex indicated that the compound undergoes complete decomposition to form the Cr2O3 as the final decomposition product.
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    Synthesis, structural characterization, and photoluminescence properties of Eu3+-doped Mg3-xEux(BO3)(2) phosphor
    (Wiley, 2018) Morkan, Ayşe Uztetik; Gül, Esra
    Eu3+-doped Mg3-xEux(BO3)(2) (x=0.000, 0.005, 0.010, 0.020, 0.050, and 0.100) phosphors were synthesized for the first time by solution combustion synthesis method, which is a fast synthesis method for obtaining nano-sized borate powders. The optimization of the synthesis conditions of phosphor materials was performed by TG/DTA method. These phosphors were characterized by XRD, FTIR, SEM-EDX, and photoluminescence, PL analysis. The XRD analysis exhibited that all of the prepared ceramic compounds have been crystallized in orthorhombic structure with space group Pnnm. Also, the influence of europium dopant ions on unit cell parameters of host material was analyzed using Jana2006 program and the crystalline size was determined by Debye-Scherrer's formula. The luminescence properties of all Eu3+-doped samples were investigated by excitation and emission spectra. The excitation spectra of Mg3-xEux(BO3)(2) phosphors show characteristic peak at 420nm in addition to other characteristic peaks of Eu3+ under emission at 613nm. The emission spectra of Eu3+-doped samples indicated most intensive red emission band dominated at 630nm belonging to (D0F2)-D-5-F-7 magnetic dipole transition. Furthermore, the optimum or quenching concentration of Eu3+ ion has been determined as x=0.010 showed the maximum emission intensity when it was excited at 394nm.