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    Öğe
    Improvement in electrical properties of Bi-2212 superconducting materials substituted with large-scale nano-sized tin
    (Springer Heidelberg, 2024) Aytekin, Mehmet Ersin; Akyol, Mustafa; Ozkurt, Berdan
    In the current work, the effect of nano-sized Sn (50 nm)/Sr partial replacement on the superconducting properties such as crystal structure, quality of intra- and intergrain boundary coupling, dc electrical resistivity, and dc magnetization in the Bi-2212 ceramic superconductors were investigated. Ceramic superconductors with nominal composition of Bi2Sr2-x(Sn)(x)Ca1Cu1.75Na0.25Oy where x = 0.25, 0.30, 0.35 and 0.40 were prepared by solid-state reaction method and characterized by powder X-ray diffraction (XRD), dc electrical resistivity, scanning electron microscopy (SEM) and magnetic hysteresis (M-H) measurements. Phase examination of by XRD indicated that the doping of x = 0.25 ratio nano-sized SnO2 to the strontium sites improved the formation of the Bi-2212 high-temperature superconducting phase. SEM micrographs showed that the morphological structure of all samples consisted of plate-like grains, which were separated from each other by grain boundaries, indicating the Bi-2212 superconducting phase. The highest superconductivity transition temperature among the samples was measured as the T-c(onset) = 86 K at x = 0.25 in Bi2Sr2-x(Sn)(x)Ca1Cu1.75Na0.25Oy. M-H loops of the Bi2Sr2-x(Sn)(x)Ca1Cu1.75Na0.25Oy sample at x = 0.25 ratio is larger compared to other examples, indicating improvement intergrain connectivity as well as enhanced flux pinning centers. In addition, the critical current (J(c)) values of the samples were calculated from M-H measurement using Bean's critical current model. The best J(c) values were obtained as 570 A/cm(2) at 15 K, which is a relatively high value for BSCCO superconductors with polycrystalline structure.
  • [ X ]
    Öğe
    Modification of Magnetic and Electrical Properties of Bi,Pb-2223 Superconductors by Nano-Sized Eu Substitution
    (Springer, 2025) Aytekin, Mehmet Ersin; Akyol, Mustafa
    In the current paper, the effect of nano Eu particle (80 nm) substitution (x = 0.00, 0,025, 0.050, 0.1 and 0.15) in the Bi1.7Pb0.3Sr2Ca1Cu1.75Na0.25Oy on the structural, morphological, magnetic and superconductivity properties was investigated. The solid-state reaction method was used for producing the ceramic samples. The X-ray diffraction (XRD) analysis shows that the Bi-2223 phase with a tetragonal structure is the main phase structure in the ceramic samples. A flaky plate structure separated by grain boundaries has been observed in the scanning electron microscope (SEM). It was found that the grain sizes expanded and the inter-grain bonding increased when nano-sized Eu is added in the host structure. In magnetic hysteresis (M-H) measurements, diamagnetic behaviour, which is characteristic of the Bi-2223 superconductor phase, was observed in all samples. The sample with the best diamagnetic behaviour was substituted with Eu nano particle at a rate of x = 0.1, resulting in an increase in the hysteresis field with the formation of intergranular bonds. Based on M-H measurements performed at temperatures of 15 K and 25 K, the samples' critical current density (J(c)) was determined using the Bean model. The highest critical current density value was calculated in the sample substituted with nano-sized Eu at x = 0.1 rate as a result of improving intergranular connections. Flux pinning forces (F-p) were determined from J(c) and B values. Nano-sized Eu particles at a ratio of x = 0.1 improved the pinning forces by acting as flux pinning centres.