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Öğe Effect of Mn addition on structural and superconducting properties of (Bi, Pb)-2223 superconducting ceramics(Springer, 2012) Yıldırım, Gürcan; Bal, S.; Yücel, Ersin; Doğruer, Musa; Akdoğan, Mustafa; Varilci, Ahmet; Terzioğlu, CabirThis study deals with the effect of Mn addition on the structural and superconducting properties of Bi1.8Pb0.4Sr2Mn (x) Ca2.2Cu3.0O (y) ceramics with x=0,0.03,0.06,0.15,0.3 and 0.6 by means of X-ray analysis (XRD), scanning electron microscopy (SEM), electron dispersive X-ray (EDX), resistivity, and transport critical current density (J (c)) measurements. Zero-resistivity transition temperatures (T (c)) of the samples produced via the standard solid-state reaction method are estimated from the dc resistivity measurements. Moreover, the phase fraction and lattice parameters are determined from XRD measurements while the microstructure, surface morphology and element composition analyses of the samples are investigated by SEM and EDX measurements, respectively. It is found that T (c) values are obtained to decrease from 109 K to 85 K; likewise, J (c) values are observed to reduce from 3200 A/cm(2) to 125 A/cm(2) with increasing Mn addition. According to the refinement of cell parameters done by considering the structural modulation, the Mn addition is confirmed by both an increase of the lattice parameter a and a decrease of the cell parameter c of the samples in comparison with that of the pure sample (Mn0). SEM measurements show that not only the surface morphology and grain connectivity are seen to degrade but the grain sizes of the samples are found to decrease with the increase of the Mn addition as well. The EDX results reveal that the elements used for the preparation of samples distribute homogeneously and the Mn atoms enter into the crystal structure by replacing Sr and Cu atoms. The possible reasons for the obtained degradation in microstructural and superconducting properties are also interpreted.Öğe Investigation of structural and superconducting properties of Cr added Bi-2212 superconducting ceramics(Springer, 2012) Yıldırım, Gürcan; Yücel, Ersin; Bal, S.; Doğruer, Musa; Varilci, Ahmet; Akdoğan, Mustafa; Terzioğlu, CabirThis study reports the effect of Cr addition on the structural and superconducting properties of Bi(1.8)Sr(2.0)CrxCa(1.1)Cu(2.1)O (y) superconductor with x=0, 0.1, 0.3, 0.5 0.7, and 1 by means of X-ray analysis (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and resistivity measurements. The samples studied in this work were prepared using the standard solid-state reaction method. Zero resistivity transition temperatures (T (c) ) are qualitatively estimated from the dc resistivity measurements. The zero resistivity transition temperatures are obtained to decrease from 81 K to 53 K with the increase in Cr addition. Moreover, the phase and lattice parameters were determined from XRD measurements. Based on the refinement of cell parameters done by considering the structural modulation, the Cr addition was confirmed by an increase of the lattice parameter a and decrease of the cell parameter a of the samples in comparison with that of the undoped sample (Cr0). As for the microstructure and element composition analyses on the surface of the samples produced, SEM and EDS measurements were investigated. According to the measurements, not only were the grain sizes of the samples noted to decrease, but also the surface morphology and grain connectivity were obtained to degrade with increase in the Cr addition. The possible reasons for the observed degradation in microstructural and superconducting properties due to Cr addition were also discussed.Öğe Role of annealing temperature on microstructural and electro-optical properties of ITO films produced by sputtering(Springer, 2013) Gülen, Mahir; Yıldırım, Gürcan; Bal, S.; Varilci, Ahmet; Belenli, İbrahim; Öz, MuhammedThis study probes the effect of annealing temperature on electrical, optical and microstructural properties of indium tin oxide (ITO) films deposited onto soda lime glass substrates by conventional direct current (DC) magnetron reactive sputtering technique at 100 watt using an ITO ceramic target (In2O3:SnO2, 90:10 wt%) in argon atmosphere at room temperature. The films obtained are exposed to the calcination process at different temperature up to 700 A degrees C. X-ray diffractometer (XRD), ultra violet-visible spectrometer (UV-vis) and atomic force microscopy (AFM) measurements are performed to characterize the samples. Moreover, phase purity, surface morphology, optical and photocatalytic properties of the films are compared with each other. The results obtained show that all the properties depend strongly on the annealing temperature. XRD results indicate that all the samples produced contain the In2O3 phase only and exhibit the polycrystalline and cubic bixbite structure with more intensity of diffraction lines with increasing the annealing temperature until 400 A degrees C; in fact the strongest intensity of (222) peak is obtained for the sample annealed at 400 A degrees C, meaning that the sample has the greatest ratio I (222)/I (400) and the maximum grain size (54 nm). As for the AFM results, the sample prepared at 400 A degrees C has the best microstructure with the lower surface roughness. Additionally, the transmittance measurements illustrate that the amplitude of interference oscillation is in the range from 78 (for the film annealed at 400 A degrees C) to 93 % (for the film annealed at 100 A degrees C). The refractive index, packing density, porosity and optical band gap of the ITO thin films are also evaluated from the transmittance spectra. According to the results, the film annealed at 400 A degrees C obtains the better optical properties due to the high refractive index while the film produced at 100 A degrees C exhibits much better photoactivity than the other films as a result of the large optical energy band gap.Öğe Substrate effect on microstructure and optical performance of sputter-deposited TiO2 thin films(Wiley-V C H Verlag Gmbh, 2012) Yıldırım, Gürcan; Bal, S.; Gülen, M.; Varilci, Ahmet; Budak, Erhan; Akdoğan, MustafaThis study deals with the role of the different substrates on the microstructural, optical and electronical properties of TiO2 thin films produced by conventional direct current (DC) magnetron sputtering in a mixture of pure argon and oxygen using a Ti metal target with the aid of Xray diffractometer (XRD), ultra violet spectrometer (UVvis) and atomic force microscopy (AFM) measurements. Transparent TiO2 thin films are deposited on Soda lime glass, MgO(100), quartz and sitall substrates. Phase purity, surface morphology, optical and photocatalytic properties of the films are compared with each other. It is found that the amplitude of interference oscillation of the films is in a range of 77-89%. The transmittance of the film deposited on Soda lime glass is the smallest while the film produced on MgO(100) substrate obtains the maximum transmittance value. The refractive index and optical band gap of the TiO2 thin films are also inferred from the transmittance spectra. The results show that the film deposited on Soda lime glass has the better optical property while the film produced on MgO(100) substrate exhibits much better photoactivity than the other films because of the large optical energy band gap. As for the XRD results, the film prepared on MgO(100) substrate contains the anatase phase only; on the other hand, the other films contain both anatase and rutile phases. Furthermore, AFM images show that the regular structures are observed on the surface of all the films studied. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
