Düzgün, İbrahim

The original version of this article contained a mistake. Thus this erratum is presented to fix this error. The section “Funding” should read as follows: This study was funded by the Grant-in-Aid for Gümüşhane University Research Fund (GÜBAP), from the Gümüşhane University (Project Number: 13.F5120.02.1).

Düzgün, İbrahim

Y123 and Y358 high-temperature superconductor phases have experimental mass attenuation coefficients (MAC) determined at 46.5, 81, 122, 302, 356, 383, 662, 1173, and 1332 keV photon energies. The experimental values have been compared with theoretical values acquired employing the XCOM software and database. It has been observed that the theoretical and the empirical results were in perfect agreement. Also, it has been seen that the comparison of the MACs for all specimens examined with the corresponding photon energies complies with the exponential absorption law. The effective atomic numbers (Zeff) and electron densities (Nel) of Y123 and Y358 superconducting phases in different energy ranges have determined experimentally and theoretically. The Y358 superconductor specimen is a relatively better absorber than the Y123 between 40 and 100 keV.

Başoğlu, M.

In this study, three different Y358 samples were produced by the melt-powder-melt-growth (MPMG) method at different maximum grain growth temperatures of 1030 °C, 1040 °C, and 1050 °C. The differential thermal analysis (DTA), X-ray powder diffraction (XRD), magnetic levitation force, trapped magnetic field values and magnetization measurements were performed. According to the results, the highest magnetic levitation force, the highest critical current density and the highest trapped magnetic field values were obtained from the sample produced at the temperature of 1050 °C.

Başoğlu, M.; Düzgün, I.; Öztürk, A.

Superconducting specimens of Y3-xLuxBa5Cu8O18+δ (where x = 0, 0.2, 0.4, 0.5) ceramic were fabricated via the solid-state route (SSR). The structural and superconducting features of the specimens were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Measurements and calculations were carried out for electrical resistance (R-T) and DC magnetization (M-H). The onset critical transition temperature (Tconset) of the specimens dropped to lower temperatures with the addition of lutetium (Lu). The estimated critical current density (Jc) values of the specimens, depending on the magnetic field, were extracted from the DC magnetization data. The changes in average grain size and bulk critical current density were examined. Improvement was observed in the bulk critical current density with increasing levels of Lu/Y substitution.

Öztürk, Ali; Düzgün, İbrahim; Başoğlu, Mehmet; Çelebi, Selahattin

Partial Re (rare earth elements: Lu, Yb and Dy) substituted YBaCuO (123) superconductors synthesized by solid-state reaction (SSR) procedure have been investigated via x-ray diffraction, scanning electron microscopy, a.c. magnetic susceptibility, and d.c. magnetization, and calculations. The measurements of a.c. magnetic susceptibility have been carried out at constant a.c. field amplitude and constant frequency for the samples studied. The temperature dependence of intergranular critical current density (Jcm) has been estimated from the a.c. magnetic susceptibility data. The d.c. magnetization measurements were performed at the temperatures of 5 K, 20 K, and 77 K separately. The variation of critical current density (Jc) with magnetic field (μ0H) has been evaluated from the d.c. magnetization data by using upper and lower branch of the major hysteresis curve. Lu substituted Y0.5Lu0.5BCO (123) sample shows higher critical current density than Yb and Dy substituted samples at low-temperature (lower than 77 K) regions.

Başoğlu, M.; Düzgün, İ.

Y3Ba5Cu8O18 (Y358) which is the last family member of YBCO superconducting material was produced by a solid-state reaction technique. During the production process, superconducting samples were sintered in different atmosphere conditions. XRD measurements of the samples were performed. As a result of the measurements, it was seen that the superconducting phase peaks were formed. Hysteresis loops were calculated and analyzed in the framework of a critical state model including the Meissner current. Meissner currents (IM) were calculated as 0.0062, 0.0037, and 0.0119 for S100, S50, and S0, respectively. It was observed that S50 has the highest critical current density among the other calculated values.

Öztürk, Ali; Doğan, Mustafa; Düzgün, İbrahim; Çelebi, Selahattin

The effect of dysprosium (Dy) doping on yttrium barium copper oxide (YBCO) prepared by conventional solid-state reaction method has been investigated by means of XRD, AC susceptibility, and DC magnetization measurements. AC susceptibility measurements for sintered YBCO pellets have been performed as a function of temperatures at constant frequency and AC field amplitude in the absence of a DC bias field. DC magnetization measurements were done at 5, 20, and 77 K upon zero field cooling (ZFC) process. The magnetization measurements showed a paramagnetic behavior existing at high magnetic fields. The magnetic field dependence of critical current density of the samples has been estimated from DC magnetization data. The partial Dy substitution for Y on YBCO superconductors improves the bulk critical current density at high magnetic fields and at high-temperature regions (higher than 20 K).

Çelebi, S.; Ozturk, A.; Uysal, E.; Kutuk, S.; Duzgun, I.

The evolution of the rate of flux creep along the major hysteresis envelopes in a Y0.5Lu0.5Ba2Ca3Oy sample synthesized by a modified melt powder melt growth (MPMG) method at 25 K has been investigated. Magnetic relaxation rates depend strongly on the prior magnetic history. Calculations based on the critical state model can reproduce quite well the experimental data for magnetization when we have chosen the field exponent n = 0.3 in critical current density, Jc(Ha) = Jc0/(Ha−IM)n, where IM = Ha when 0 < H < Hc1 and (Formula presented.) when Ha ≥ Hc1. Using the field-cooled magnetization MFC data as well as the comparison of experimental and calculated M–H hysteresis loop, we estimated Hc1 = 500 Oe, p = 0, and the penetration field H∗ = 20 kOe. The apparent pinning energy was estimated as 62 meV for the remanent magnetization upon an excursion of 40 kOe.

Başoğlu, M.; Yanmaz, E.

Sintered Nd-Fe-B magnets are some of the strongest magnetic materials showing magnetic properties. Blending addition is frequently performed in order to improve the magnetic properties of these materials. In this work, high-melting point Ni and low-melting point Cu were added to Nd15Fe77B8 ingot by blending. As a result of structural analysis, it was observed that 0.2 wt% Cu + Ni addition improved the structure of the material; on the other hand, excessive addition resulted in porosity. It was also observed that 0.2 wt% addition improved the magnetic properties, and Curie temperature increased with increasing addition ratio.