Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Author: search.filters.author.Kocabaş, KemalSubject: search.filters.subject.X-ray diffraction

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  • Article
    Citation - WoS: 10
    Citation - Scopus: 11
    The Effects of Sb Substitution on Structural Properties in Yba 2cu 3o 7 Superconductors
    (Springer Verlag, 2011) Akyüz, Gönül B.; Kocabaş, Kemal; Yıldız, Aylin; Özyüzer, Lütfi; Çiftçioglu, Muhsin
    In this study, the effects of partial Sb 3+ ion substitutions for the Y sites and the Cu sites on the superconducting properties of YBa 2Cu 3O y (Y123) ceramic superconductors were investigated. The samples were prepared by the conventional solid-state reaction method and the properties of the samples were investigated by means of X-ray diffraction, AC magnetic susceptibility measurements, scanning electron microscope, and energy dispersive X-ray analysis. The critical temperatures were determined to be in the range of 80-92 K for both Systems I and II. It was found that Sb-addition leads to the formation of the non-superconducting YBa 2SbO 6 phase, which has a negative effect on the critical temperature, since the highest critical temperature was measured for pure Y123. However, the increasing substitution level has a negligible effect on the X-ray diffraction analysis peak intensities of the superconducting phases. In addition, SEM images showed that Sb substitution decreases the grain size and modifies the microstructure development, which makes the samples denser.
  • Article
    Citation - WoS: 89
    Citation - Scopus: 94
    Effects of Li Substitution in Bi-2223 Superconductors
    (Springer Verlag, 2008) Bilgili, Özlem; Selamet, Yusuf; Kocabaş, Kemal
    The effects of Li substitution on the properties of high temperature superconductor Bi 17Pb 0.3Sr 2C 2Cu 3-x Li x O y were investigated. The samples were prepared by substituting Li (x=0.00-0.20) with changing ratios by a solid state reaction method. The samples were characterized by X-ray diffraction, DC electrical resistivity, AC magnetic susceptibility, and scanning electronic microscopy (SEM). The X-ray diffraction studies were done at room temperature and the lattice constants of the material were determined by indexing all the peaks observed. This study shows that there are two coexisting phases; high-T c (2223) phase and low-T c (2212) phase. The lattice structure of the material belongs to the orthorhombic unit cell. The volume fraction was estimated from the intensities of Bi-(2223) and Bi-(2212) phases. The sample with 20 wt% of added Li showed the higher volume fraction of Bi-(2223) phase formed (81%) compared to the other samples. The DC electrical resistivity of all the samples decreased as the wt% of Li increased. Both the onset critical temperatures T c (onset) and zero electrical resistivity critical temperatures T c (R=0) of the samples were determined from the DC electrical resistivity measurements. The observed value of the onset critical T c (onset) temperature was 110 K agreeing well with the magnetic susceptibility measurements. We obtained T c onset at 112 K from AC magnetic susceptibility measurements. © 2008 Springer Science+Business Media, LLC.