Endüstri Mühendisliği Bölümü / Department of Industrial Engineering

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Browsing Endüstri Mühendisliği Bölümü / Department of Industrial Engineering by Publisher "Elsevier Science Sa, Po Box 564, 1001 Lausanne, Switzerland"

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    Frequency and temperature dependent electrical and dielectric properties of LaCrO3 and Ir doped LaCrO3 perovskite compounds
    (Elsevier Science Sa, Po Box 564, 1001 Lausanne, Switzerland, 2018-04-05) Coşkun, M.; Coşkun, F. M.; Durmuş, Zehra; Çağlar, Müjdat; Turut, Abdulmecit; POLAT, ÖZGÜR; 110485; 21994; 3726
    Perovskite oxide materials, especially perovskite lanthanum chromium oxide, LaCrO3 (LCO) have taken considerable attention among the scientists due to the changing optical, electrical, dielectric and magnetic properties depending on doping via various elements. In this study, the LCO and iridium (Ir) doped LCO (LaCr1-xIrxO3) (x = 0.10) compounds were synthesized using solid-state reaction method. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) have been employed to study particle morphologies and oxidation states of synthesized powders, respectively. Frequency-depended electrical/dielectric properties of perovskite oxide samples were performed in wide range frequency (1Hz-10 MHz) and temperature (-100 degrees C to +100 degrees C) using dielectric/impedance spectrometer. Electrical measurements have underscored that the dielectric constant of LCO compound dramatically decreased after doped with Ir. Furthermore, it was observed that ac conductivity and capacitance value of LCO decreased while impedance increased after Ir doping due to i) Ir occupation in Cr sites and ii) lattice distortion owing to doping larger ion Ir4+ into smaller Cr3+ ion in the LCO lattice. Finally, overlapping large polaron tunneling (OLPT) and quantum mechanical tunneling (QMT) conduction mechanisms were suggested for LCO while the correlated barrier hopping (CBH) and QMT conduction mechanisms were observed for Ir doped LCO compound. Moreover, the activation energy values have been calculated by employing both f(max) vs. 1/T and sigma(dc) vs. 1/T plots. It has been shown those energy values are in good agreement with each other for LCO and Ir doped LCO samples at various temperature ranges. (C) 2018 Elsevier B.V. All rights reserved.
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    Os doped YMnO3 multiferroic: A study investigating the electrical properties through tuning the doping level
    (Elsevier Science Sa, Po Box 564, 1001 Lausanne, Switzerland, 2018-07-05) Coşkun, Merve; Durmuş, Zehra; Çağlar, Müjdat; Turut, Abdulmecit; POLAT, ÖZGÜR; 110485; 21994; 3726
    Previously, it has been demonstrated the electrical and magnetic properties of YMnO3 (YMO) can be tuned with substitution of different elements into Y and/or Mn sites. In this study, the electrical properties of YMO were explored via substituting osmium (Os) into Mn site with various mol %. The crystalline morphology of synthesized YMnO3 and YMn1-xOsxO3 (YMOO) (x = 0.01, 0.05, 0.10) powders were characterized with X-ray diffractometer (XRD) and infrared spectroscopy (IR) measurements. The crystalline morphology of synthesized powders was studied via scanning electron microscope (SEM). Oxidation states of constituent elements have been examined by X-ray photoelectron spectroscopy (XPS). Electrical properties of YMO and YMOO powders were investigated by dielectric/impedance spectrometer at various temperatures and frequencies. Electric modulus measurements unveiled that for each of x = 0, 0.01 and 0.05 samples there are three relaxation peaks while x = 0.10 sample shows four relaxation peaks. It has been shown that dielectric constant and conductivity properties of parent YMO can be enhanced via Os substitution, particularly, 10 mol % Os doped sample has the highest dielectric constant and conductivity at various temperatures and frequency regions. Moreover, the conduction mechanisms were also examined. It turned out that in order to explain conduction mechanism, multiple models need to be considered in the studied materials. (C) 2018 Elsevier B.V. All rights reserved.