Yazar "Almessiere, M.A." seçeneğine göre listele

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  • Küçük Resim
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    Frequency and dc bias voltage dependent dielectric properties and electrical conductivity of BaTiO3-SrTiO3/(SiO2)(x) nanocomposites
    (Elsevier Sci Ltd, 2019) Slimani, Yassine; Ünal, Bayram; Hannachi, Essia; Selmi, Aymen; Almessiere, M.A.; Nawaz, Muhammad; Yıldız, M.
    BaTiO3-SrTiO3/(SiO2)(x) nanocomposites (x = 0, 0.5, 1, 2 and 5%) were produced through solid state reaction. The morphological, structural, spectral, and optical properties were investigated by scanning electron microscope, X-ray powder diffraction (XRD), Fourier transform-infrared spectroscopy and ultraviolet-visible diffuse reflectance spectrophotometry, respectively. All XRD patterns illustrate two distinct phases of BaTiO3 and SrTiO3 with cubic structure. No impurity was noticed for x <= 0.5% nanocomposite. However, Ba2TiSi2O8 secondary phase starts to appear for x >= 1%. Electrical and dielectric properties were used to analyze the dielectric constant and loss, the conductivity as well as dissipation factors as functions of both frequencies and dc bias voltage for BaTiO3-SrTiO3/(SiO2)(x) nanocomposites. In general, conductivity and dielectric loss obey power law tendencies against frequencies. However, the dc bias was found to be less effective to conduction mechanism having a slight change for a variety of SiO2 percentages.
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    The impact of Eu3+ ion substitution on dielectric properties of Y3-xEuxAl5O12 (0.00x0.10) ceramics
    (Springer, 2019) Almessiere, M.A.; Ünal, Bayram; Baykal, Aslıhan; Ercan, I.; Yıldız, M.
    This study reported the effect of Eu substitutions on the conductivity and dielectric properties of Y3-xEuxAl5O12 (0.0x0.1), YAG:xEu(3+). All products were fabricated by solid state route. The formation of YAG was approved through X-ray diffraction powder diffraction and high-resolution transmission electron microscope. It was found that the lattice parameters are increasing with increase the substitution content due to the difference in ionic radii between Y3+ and Eu3+. Electrical and dielectric properties of YAG (Y3Al5O12) and YAG:xEu(3+) ceramics were investigated extensively for a variety of concentrations (0.00x0.1) of the substitutional Eu3+ ion from the 4f lanthanide group. The temperature dependence of dielectric loss, dielectric constant, loss tangent and ac/dc conductivity were examined up to 5.0MHz to understand the electrical and dielectric properties for both doped and undoped YAG ceramics. The experimental results revealed that Eu3+ ion substitutions (especially x=0.05) in YAG ceramics meaningfully influence the lossy mechanisms, conductivity and dielectric constant which is probably due to the contribution to the conduction mechanism of the 4f-Eu and 3d-Al ions. So, this can be incorporated at the exceptional sites of both O-h (octahedral) and T-d (tetrahedral) symmetries in YAG: xEu(3+) ceramics.