Yazar "Coskun, F. M." seçeneğine göre listele

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    A comprehensive investigation of the structural, chemical, and dielectric properties of co-doped YMnO3 multiferroic component
    (Springer Heidelberg, 2024) Polat, O.; Coskun, M.; Yildirim, Y.; Coskun, F. M.; Durmus, Z.; Sen, C.; Caglar, Y.
    The solid-state reaction technique was employed to synthesize compounds of YMnO3 (YMO) and YMn1-xCoxO3 (YMCO) with various Co doping levels (x = 0.01, 0.10, 0.20, and 0.40), where Co atoms partially substituted Mn sites. XRD studies confirmed the presence of two phases, YMO and Y0.98CoO3 (YCO), for doping ratios above x = 0.10. Additionally, an increase in crystalline size was observed with cobalt substitution. Surface characteristics of synthesized pellets were examined using scanning electron microscopy (SEM), revealing a less porous structure with cobalt doping. XPS analysis elucidated valence states, showing the presence of both Mn3+ and Mn4+, as well as Co2+ and Co3+. The x = 0.20 and 0.40 Co-doped samples exhibited lower grain and grain boundary energies compared to other samples, such as a decrease from 0.556 eV (undoped) to 0.195 eV (x = 0.20). Moreover, the dielectric constants of x = 0.20 and 0.40 cobalt-doped samples (around 320) significantly surpassed the undoped sample (around 22) at 10(6) Hz and 100 degrees C. The x = 0.20 cobalt-doped sample demonstrated the highest conductivity at 100 degrees C and 10(6) Hz (31 x 10(-4) S/cm). FT-IR analysis provided insights into vibration and bending modes, and frequency- and temperature-dependent electrical features were investigated. It was observed that a single conduction model is insufficient to fully explain the conduction mechanism in these samples.
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    The structural studies and optical characteristics of phase-segregated Ir-doped LuFeO3-? films
    (Springer Heidelberg, 2023) Polat, O.; Coskun, F. M.; Yildirim, Y.; Sobola, D.; Ercelik, M.; Arikan, M.; Coskun, M.
    In this work, we carefully examined how Ir substitution into Fe sites can change the band of the LuFeO3 (LFO) material. LFO and Ir-doped LFO (LuFe1-xIrxO3 or LFIO for short, where x = 0.05 and 0.10) thin films were synthesized by utilizing magnetron sputtering techniques. The films were grown on silicon and indium tin oxide (ITO) substrates at 500 degrees C. The crystallographic orientation of the films was examined using X-ray diffraction (XRD) analysis. The crystallographic orientation of the thin films was examined using an X-ray diffractometer (XRD). For surface topography research, atomic force microscopy (AFM) was employed. To look for the recombination of photogenerated electron-hole pairs in the materials under investigation, photoluminescence (PL) spectroscopy was used. Raman spectroscopy is then utilized to gather data on crystal symmetry as well as disorders and defects in the oxide materials. It was demonstrated that the LFO band gap was altered from 2.35 to 2.72 eV by Ir substitution into Fe sites. Moreover, diffuse reflectance spectroscopy (DRS) was used to analyze conductivity, real and imaginary components of the dielectric constant, refractive index (n), extinction coefficient (k), and reflectance percentage.