Yazar "Terzioglu, Cabir" seçeneğine göre listele

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    Development of modulation, pairing mechanism, and slip system with optimum vanadium substitution at Bi-sites in Bi-2212 ceramic structure
    (Elsevier Science Sa, 2023) Ulgen, Asaf Tolga; Okur, Semih; Erdem, Umit; Terzioglu, Cabir; Turgay, Tahsin; Turkoz, Mustafa Burak; Yildirim, Gurcan
    Present study focuses extensively on the change in electrical, superconducting and microhardness parameters with partial substitution of trivalent V+3 impurities replacing Bi+3 ions in Bi-2212 ceramic compound with the aid of dc electrical resistivity and microhardness test measurements. Experimental findings, calculation results, and phenomenological discussions provide that the optimum vanadium substitution level is found to be x = 0.01 in the Bi2.0-xVxSr2.0Ca1.1Cu2.0Oy (Bi-2212) ceramic system for the highest conductivity, crystallinity quality, superconducting, and mechanical performance features depending on the decreased microscopic structural problems. All the findings are wholly verified by scanning electron microscopy (SEM) and X-Ray diffraction (XRD) analyses. The dc electrical measurements indicate that the optimum vanadium ions support the pairing mechanism for the formation of new polaronic states in the clusters of microdomains, and hence expand superconducting energy gap due to the enhancement of amplitude part of pair wave function in the spin-density wave systems. The excess vanadium content degrades all the basic thermodynamics and quantum mechanical quantities mentioned due to the stress-induced phase transformation. Numerically, the Bi-2212 advanced ceramic matrix prepared by the optimum vanadium impurity is noticed to present the smallest residual resistivity value of 0.08 m & omega; cm, room temperature resistivity value of 8.84 m & omega; cm, and broadening degree of 0.36 K. Similarly, the ceramic material is found to possess the highest residual resistivity ratio of 3.05, carrier concen-tration number of 0.153041, critical transition offset and onset value of 84.66 K and 85.02 K, respectively. Besides, the microhardness findings reveal that the same compound with the least sensitivity to the applied test loads exhibits the largest Hv value of 4.799 GPa, Young's moduli of 393.303 GPa, yield strength of (0.969 GPa), and elastic stiffness coefficient of 15.5574 (GPa)7/4 under the applied test load of 0.245 N. The XRD in-vestigations show that the presence of optimum vanadium impurity supports the formation of a high super-conducting phase, c-axis length, and average crystallite size. All the findings are morphologically confirmed by the SEM images. It is found that the crystallographically best crystallinity quality and view of surface morphology is observed for the optimum vanadium substitution level. All in all, new higher properties for the conductivity, crystallinity quality, surface morphology, superconducting, and microhardness parameters based on the optimum vanadium replacement encourage the Bi-2212 crystal system to use in much more application places.
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    Experimental and theoretical approaches on magnetoresistivity of Lu-Doped Y-123 superconducting ceramics
    (Springer, 2013) Türköz, Mustafa Burak; Nezir, Saffet; Varilci, Ahmet; Yıldırım, Gürcan; Akdogan, Mehmet; Terzioglu, Cabir
    This study discusses the change of the flux pinning mechanism, electrical and superconducting properties of Lu added YBa2Cu3O7-delta bulk superconducting ceramics prepared by the liquid ammonium nitrate and derivatives at 970 A degrees C for 20 h by means of magnetotransport measurements conducted in the magnetic filed range from 0 to 6 kG. The critical transition (both and) temperatures, residual resistivity (rho(0)), residual resistivity ratios (RRR), irreversibility fields (mu H-0(irr)), upper critical fields (mu (0) H (c2) ), penetration depths (lambda) and coherence lengths (xi) of the YBa2LuxCu3O7-delta materials are evaluated from the magnetoresistivity curves. The resistivity criteria of 10 and 90 % normal-state resistivity serve as the important parameters for the description of the irreversibility and upper critical fields, respectively. Moreover, rho (0) , mu (0) H (irr) (0) and mu (0) H (c2) (0) values of the bulk samples are theoretically calculated using the extrapolation method at absolute zero temperature (T = 0 K). Likewise, the xi and lambda values are inferred from mu (0) H (irr) (0) and mu (0) H (c2) (0) values obtained, respectively. At the same time, activation energies of the samples studied are determined from thermally activated flux creep (TAFC) model. The results obtained indicate that the pinning mechanism, electrical and superconducting properties of the samples enhance with the increment of the Lu addition up to level of 0.1 wt% beyond which these properties start to deteriorate systematically and in fact reach the local minimum points for the sample doped with 0.9 wt% Lu due to the degradation of pinning ability, density, crystallinity and connectivity between grains. Similarly, the presence of the magnetic field results in the reduction of these properties as a consequence of the decrement in the flux pinning in the samples prepared. Namely, the maximum of 94.6 K and of 92.5 K are observed for the sample doped with 0.1 wt% Lu whereas the minimum temperature values are obtained to be about 71.2 and 50.3 K for the sample doped with 0.9 wt% Lu. In fact, the value decreases to 20.5 K with the increment in the applied magnetic field up to 6 kG. Besides, the flux pinning energies of the samples decrease with ascending applied magnetic field. The pure sample has the flux pinning energy of 15,211 K at zero field while the maximum and minimum values are found to be about 16,722 K and 2,058 K for the samples added with 0.1 and 0.9 wt% Lu, respectively. The U (0) of 158 K at 6 kG applied magnetic field is obtained for the latter sample, showing that this sample exhibits much weaker flux pinning, lesser crystallinity and connectivity between grains compared to the other samples produced as a result of the stronger pair-breaking mechanism. The dissipation mechanism is also discussed by means of the magnetic field dependence of the activation energy.
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    Improvement in deformation degree of Zr surface-layered Bi-2223 ceramics by diffusion annealing temperature
    (Elsevier Sci Ltd, 2023) Mercan, Ali; Terzioglu, Rifki; Dogan, Muhsin Ugur; Kaya, Senol; Erdem, Umit; Yildirim, Gurcan; Terzioglu, Cabir
    This study investigated the effects of different annealing temperatures (650 degrees C <= T <= 840 degrees C) on the surface morphological and mechanical performance properties of Zr surface-layered Bi-2223 materials with scanning electron microscopy (SEM) images, Vickers microhardness (Hv) measurements, and semi-empirical mechanical approaches. It was observed that the ceramic compound exposed to 650 degrees C annealing temperature exhibited the superior performance features due to the enhancement in the deformation degree. This is because the Zr ions behaved as the nucleation centers to prevent the propagations of cracks and dislocations throughout the main matrix depending on the decrease in the degree of granularity and distributions of crystal structure problems over a wider area. Similarly, the SEM pictures indicated that the diffusion mechanism increased the random distributions of the thinner plate-like granular structures (serving as nucleation centers), leading the decrease in the coupling problems between the grains. Among the materials, the highest surface densification was observed for the compound exposed to 650 degrees C. Namely, surface morphological analysis showed a strong correlation be-tween microstructure and mechanical performances. Further, the zirconium ions were found to decrease in the non-recoverable stress concentration sites, crack-initiating defects, and dislocations in the ceramic system. Accordingly, the sensitivity to the applied test load was noted to decrease dramatically. Shortly, crack growth size and velocity were observed to be more easily under control. Correspondingly, the Zr ions delayed consid-erably the beginning points of saturation limit (load-independent) regions for the bulk Bi-2223 superconducting materials. Additionally, the Zr ions led to the change in the mechanical characteristic behavior from typical indentation size effect to reverse indentation size effect. Lastly, the microindentation hardness measurements were semi-empirically analyzed by the different models. According to the comparison, Hays-Kendall mechanical model was noted to provide the closest parameters to the load-independent microhardness results.
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    Investigation of Sm → Ca substitution in Bi(Pb)SrCaCuO high temperature superconductor by low field AC magnetic susceptibility
    (Springer, 2007) Terzioglu, Cabir; Yegen, Dincer; Yilmazlar, Mustafa; Görür, Osman; Akdogan, Mustafa; Varilci, Ahmet
    We have investigated the effect of Sm substitution in Bi(Pb)SrCaCuO system by performing AC susceptibility (chi = chi' + i chi ''), XRD (X Ray Diffraction) and SEM (Scanning Electron Microscopy) measurements. The Sm -> Ca substitution (Bi(1.)6Pb(0.4)Sr(2)Ca(2-x)Sm(x)Cu(3)O(y)) was carried out by conventional solid-state reaction method. The susceptibility measurements were carried out at different values of the AC field amplitudes. The imaginary part of susceptibility is used to estimate the intergranular critical current density by means of the Bean's model. The intergranular critical current density (J(c)) of pure sample is found to be about 68 A/cm(2) at 95 K. The intergranular J(c) is seen to decrease with increasing Sm substitution. XRD pattern and SEM micrographs are given to provide information about Bi-2223 phase and grain size respectively.
  • Küçük Resim
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    Structural and physical properties of Sm-doped Bi1.6Pb0.4Sr2Ca2-xSmxCu3Oy superconductors
    (Elsevier Science Bv, 2005) Terzioglu, Cabir; Yilmazlar, Mustafa; Öztürk, Özgür; Yanmaz, Ekrem
    The superconducting Bi1.6Pb0.4Sr2Ca2-xSMxCu3Oy (X = 0.0, 0.0005, 0.001, 0.005, 0.01, 0.1, 0.5, 1.0, and 1.5) system was investigated for different concentrations of Sm. The structural analysis was carried out by XRD. XRD results show that the samples with substitution of various amounts of Sm for Ca transform from the major high-T-c phase (Bi-2223) to the low-T-c phase (Bi-2212). The lattice parameter data extracted from XRD showed that with increasing Sm concentration (x), the lattice parameter a increases slightly while the lattice parameter c decreases significantly. DC resistivity measurements were carried out by the standard four-probe technique in the temperature range between 25 K and 130 K. With increasing Sm substitution up to x = 0.1, the values of T-e(offset) vary between 107 K and 70 K. The samples with x > 0.1 did not show any superconducting transition down to 25 K. The critical current density measurements were performed in liquid nitrogen. Critical current density decreases with increasing Sm substitution, and it was measured to be 43 A/cm(2) for the sample with x = 0.0 at zero field. Microstructure examinations were carried out by SEM. All the reported data were discussed, and compared with earlier results on Sm and other substituted Bi-Sr-Ca-Cu-O system. (c) 2005 Elsevier B.V. All rights reserved.
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    Variation of fundamental features of cobalt surface-layered Bi-2212 superconductor materials with diffusion annealing temperature
    (Elsevier Sci Ltd, 2023) Oz, Ilker; Terzioglu, Cabir; Oz, Muhammed; Ulgen, Asaf Tolga; Turkoz, Mustafa Burak; Erdem, Umit; Yildirim, Gurcan
    The present study appears extensively on the role of diffusion annealing temperature intervals 650-850 degrees C on electrical conductivity, flux pinning ability, superconducting and crystallinity quality of Cobalt (Co) surface -layered Bi-2212 compounds with experimental tests including dc resistivity, bulk density, X-ray diffraction, critical current density measurements, and theoretical calculations. Experimental findings display that the Co ions may be replaced mostly by bismuth sites in the crystal lattice as a consequence of appropriate cation -vacancy, electron configurations of the outer shell, chemical valence states, and electronegativity of chemical contents in the main composition. The fundamental characteristic features refine considerably with 650 degrees C annealing temperature due to enhancement of antiferromagnetic spin fluctuations in the clusters of micro -domains, re-ordering of Cu-O bonds, stabilization of system, pairing mechanism, modulation of insulating Bi-O double layers, and orbital hybridization mechanisms. Accordingly, bulk Bi-2212 ceramic obtained at optimum annealing temperature exhibits the best conductivity because of a decrease in systematic crystallinity problems and potential grain boundary interaction problems expected in the system. Likewise, the optimum annealing temperature triggers the artificial nucleation regions for 2D discrete pancakelike Abrikosov vortices to decelerate thermal fluxon movements. Moreover, the X-ray diffraction results indicate that optimum Co ions in crystal lattice significantly improve crystal structure quality, grain alignment distributions in c-axis orientation, the extension of high-Tc Bi-2223 superconducting phase, and average crystallite size parameters. Additionally, the nucleation activation energy is noticed to reduce with optimum Co ions due to enhancement in the nucleation stability and crystallization temperature values to higher temperature zones. Namely, optimum Co ions easily diffusing into the lattice points support the formation of surface nucleation. In contrast, after a critical value of 650 degrees C, the characteristic properties mentioned suppress remarkably. In conclusion, the main characteristic features are extensively improved by the optimum diffusion annealing temperature for usage in novel and feasible market areas.