Pinning properties of Y211 added cold top-seeded YBCO grown on Y2O3 layer

onference: International Physics Conference at the Anatolian Peak (IPCAP) Location: Ataturk Univ, Nenehatun Cultural Ctr, Erzurum, TURKEY Date: FEB 25-27, 2016In this study, samples having different composition were prepared with the cold top seeding-melt-growth (TSMG) process by using Nd123 seed. Y2O3 buffer layer was placed to bottom of the pellets consist of Y123: Y211 powder mixtures. Two samples were fabricated in stoichiometric ratios of 1:0 and 1:0.4 labeled as Y0 and Y40, respectively. The T-c onset values of Y0 and Y40 were found to be 93.4 and 93.6 K at 0 T, respectively. The dependence of the effective activation energy U of the flux pinning on the magnetic field and temperature of the sample were determined using the Arrhenius activation energy law from the resistivity curves. The magnetization measurements were performed using a vibrating sample magnetometer (VSM) at 30, 50 and 77 K. The critical current densities (J(c)) for Y0 and Y40 samples were determined to be 5.1x10(3) and 3.7x10(3) A/cm(2) at 77 K in 0 T, respectively. The normalized pinning force density versus the reduced field was examined at different temperatures to determine the pinning mechanism.Ataturk Univ, Phys Dep

The effect of excess Y2O3 addition on the mechanical properties of melt-processed YBCO superconductor

In this study, two kinds of melt-processed YBCO samples with Y2O3 addition were fabricated and their microstructures were defined by XRD analysis and polarized light optical microscopy. The mechanical properties of these compounds have been investigated by measuring the Vickers hardness. The superconducting transition temperature was determined by inductive measurements for oxygenated and non-oxygenated samples. The compacted powders were located on a crucible with a buffer layer of Y2O3 and a crucible with Y2O3 powder freely poured to avoid liquid to spread on the furnace plate. It was found that the sample located on crucible with freely poured Y2O3 powder has shown almost single crystal and indicated a very sharp transition curve

The Effect of Y2O3 on AC susceptibility measurements of MPMG YBCO superconductor

Meeting: 3rd International Conference on Superconductivity and Magnetism (ICSM) Location: Istanbul, TURKEY Date: APR 29-MAY 04, 2012In this study, two kinds of melt-powder-melt-growth (MPMG) YBCO sample grown on a buffer layer of Y2O3 addition were fabricated. The compacted powders were located on a crucible with Y2O3 powder freely poured and a buffer layer of pressed Y2O3. AC susceptibility measurements of the samples as a function of temperature was reported for several different AC magnetic-field amplitudes (H (ac) ) in the presence of static bias magnetic field (H (b) ) directed along H (ac) . The loss peaks are found to shift towards lower temperatures as the AC field strength is increased. The frequency effect on the AC susceptibility was also measured. As the frequency increases, the peak temperature shifts to higher temperature. This effect can be interpreted in terms of flux creep

Structural and magnetic properties of the ring shaped 40 wt% Y211 added TSMG Y123 bulk superconductors welded by Ag2O added MPMG YBCO solder material

In this study, two 40% Y211+Y123 bulk superconductors named Y-1 and Y-2 were fabricated by cold top seeding-melt-growth (TSMG) method by using a Nd123 seed with Y2O3 buffer layer placed to bottom of the pellets. The samples were welded with 17 wt% Ag2O+Y123 bulk sample named Y-Ag using as a solder material with a lower decomposition temperature and is produced by melt-powder-melt-growth process (MPMG) with Y2O3 buffer layer. Small specimens were cut above, below and on welding regions of the welded sample and were named as Y-a, Y-b and Y-ab, respectively. The welded solder material and welded samples were studied with XRD, SEM structural analysis, resistivity and magnetization measurements. The welding region was mechanically durable and supported the critical current density (J (c) ) across the joints. The interface of the parent bulk surface and the epitaxially nucleated interfaces are very clean and no residual liquid phases or defects are observed. The onset (T (c,onset) ) and offset (T (c,offset) ) critical temperatures and upper critical fields (H (c2) ) of the samples were evaluated from the magneto resistivity curves. Below the superconducting onset temperature of around 93 K, all samples exhibit sharp superconducting transition with their T (c) (R ae 0) of around 92 K at the 0 T magnetic field, showing that the welding process had no disruptive effect on T (c) . The H (c2) (0) values were 175, 133 and 91 T for Y-a, Y-ab and Y-b respectively. The calculated J (c) values of Y-a, Y-b and Y-ab were 3.71, 3.38 and 3.08 kA/cm(2), respectively, in 0 T field at 77 K. It was obtained that, the J (c) value of the welding region is the comparable to the welding bulks. As a result, we have succeeded in producing a strongly coupled superconducting YBa2Cu3O7-x joint by combining two bulk superconductors of TSMG Y123 by using a 17 wt% Ag2O added MPMG Y123 solder material.Karadeniz Technical University Research Grant: BAP 02- 1358

The effect of using different y2o3 layers on the activation energy and ırreversibility line of mpmg ybco bulk at 1050 degrees c growth temperature

In this study, three kinds of YBCO samples which are named Y1, Y2 and Y3 were fabricated by a melt–powder–melt–growth (MPMG) method. The Y1 sample was placed into a platinum (Pt) crucible without Y2O3, the Y2 sample was located on a Al2O3 crucible with a freely poured Y2O3 powder and the Y3 sample was located on a Al2O3 crucible with a 1-mm-thick buffer layer of Y2O3. YBCO samples were investigated by magnetoresistivity (ρ–T ) measurements in dc magnetic fields (parallel to the c-axis) up to 5 T. The effect of the Y2O3 layer on the activation energy and irreversible flux of the samples was studied. The activation energies (U ) were determined using the Arrhenius activation energy law from ρ–T . The power law relationship for U with H −α was investigated. α was calculated to find out which defects were dominant in the samples. Irreversibility fields (Hirr) and upper critical fields (Hc2) were obtained using 10 and 90% criteria of the normal-state resistivity value from ρ–T curves. Irreversibility lines (ILs) were estimated from the equation Hirr ∼ (1−Tirr(H )/Tirr(0))n. The fitting results to giant flux creep and vortex glass models were discusse

The effect of growth temperature on the irreversibility line of MPMG YBCO bulk with Y2O3 layer

This study was supported by the Turkish Scientific and Research Council (TUBITAK) research grant (TBAG-107T751) and Karadeniz Technical University - Turkey research grant (BAP 2008.111.001.8).In this study, three kinds of YBCO samples which are named Y1040, Y1050 and Y1060 were fabricated by Melt-Powder-Melt-Growth (MPMG) method without a seed crystal. Samples seem to be single crystal. The compacted powders were located on a crucible with a buffer layer of Y2O3 to avoid liquid to spread on the furnace plate and also to support crystal growth. YBCO samples were investigated by magnetoresistivity (rho-T) and magnetization (M-T) measurements in dc magnetic fields (parallel to c-axis) up to 5 T. Irreversibility fields (Him) and upper critical fields (11,2) were obtained using 10% and 90% criteria of the normal state resistivity value from rho-T curves. M-T measurements were carried out using the zero field cooling (ZFC) and field cooling (FC) processes to get irreversible temperature (T-irr). Fitting of the irreversibility line results to giant flux creep and vortex glass models were discussed. The results were found to be consistent with the results of the samples fabricated using a seed crystal. At the fabrication of MPMG YBCO, optimized temperature for crystal growth was determined to be around 1050-1060 degrees C. (C) 2017 Elsevier Ltd. All rights reserved

Fluctuation-induced conductivity analysis of Y2O3-layered YBCO single crystal

In this work, a cylindrical YBa2Cu3O7-x (Y123) sample having 20 mm diameter and 8 mm height was prepared by the cold-seeding method using an Nd123 seed, and the crystal growth process was performed in an alumina crucible with a Y2O3 layer. The structural orientation of the specimens was measured by an X-ray diffractometer (XRD). As a result of the X-ray diffraction data, only (00 l) peaks were observed, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Resistivity measurements of a 1.5-mm-thick rectangular sample were performed by a standard four-probe method at temperatures between 60 and 100 K at a rate of 4 K/min using a Physical Properties Measurement System (PPMS) under various constant magnetic fields from 1 to 5 T with the magnetic field parallel to the c-axis, which is the direction of pressing into the zero-field cooling regime (ZFC). Fluctuation-induced conductivity analysis was performed to investigate the availability of the sample for technology. The analysis showed that the critical exponents were in agreement with theoretical values; thus, it was seen that superconducting properties of the sample were good and the 3D fluctuation was dominant. Because of the large c-axis coherence length (xi (c)(0)) and small anisotropy, the superconducting properties became better. Furthermore, the fluctuations were reduced, and it was understood that the effective availability of the sample in technology will be possible.Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK): TBAG-107T751 Karadeniz Teknik University: BAP-2008.111.001.

Flux Pinning in YBCO Single Crystal Grown on Y2O3 Layer

Karadeniz Technical University research grant (BAP-2008.111.001.8).In this study, single-crystal Y123 samples were grown by a cold top-seeding method by using Nd123 seed, and the effect of Y2O3 buffer layer was investigated. The upper critical magnetic field and coherence length were established as 110 T and 17.3 ´ Å, respectively. The dependence of the effective activation energy U of the flux pinning on the magnetic field and temperature of the sample were determined using the Arrhenius activation energy law from the resistivity curves. It was found that the deduced value of the activation energy for a Y123 sample is in good agreement with the corresponding values in YBCO samples. The maximum activation energy value was approximately 0.9 eV in the zero magnetic field. In order to examine the homogeneity of the pinning properties of different layers, rectangular specimens were cut from the sample. AC susceptibility measurement was performed, and it was found that the shifting of the peak temperature (Tp) with an AC magnetic field is small, indicating good pinning properties. The normalized pinning force density versus the reduced field was examined at different temperatures to determine the pinning mechanism. It was found that normal core-type pinning was effective, and in low fields, pinning was only due to Y211 particles

Magnetic properties of the welded joined TSMG Y123+x wt% Y211 (x=20 and 30) bulk superconductors

Although the welding techniques have been used to join for bulk YBCO superconductors with a sintered superconductor, similar technique as a Ag2O added bulk YBCO superconductor fabricated by melt-powder-melt-growth process (MPMG) for using as a solder material has not been used, until now. Also, physical and the bulk superconducting properties of the welded samples have not been investigated. In this study, two 20 wt% Y211 and two 30 wt% Y211 added YBCO main samples were fabricated by cold top seeding-melt-growth (TSMG) method by using an Nd123 seed. Two main samples having the same Y211 addition and welding sample positioned between the main samples stacked and welded thermally with a pressure source simultaneously. It can be seen from the levitation force measurement, making before the welding process, that the 30 wt% Y211 added samples have the larger the maximum repulsive forces values than the 20 wt% Y211 added and Ag2O added welding samples but at the same order. After the welding process the welded samples cut into the specimens, to investigate micro structure and electromagnetic properties, positioned above, on and below of the welding region of the each welded Y123 samples. From the SEM analysis a continuous structural phase was obtained between the solder material and the main samples with a good integration without any boundary gap or defects. The welding process had no negative noticeable effect on T-c of the samples under zero magnetic field, while superconducting transition width (Delta T-c) of the specimen cutting from the 30 wt% Y211 added sample (Y30-ab) is smaller the specimen cutting from the 20 wt% Y211 added sample (Y20-ab) under applied magnetic field points out that Y30-ab is more resistant to the applied field than the Y20-ab because of the 211 addition. In addition, 30 wt% 211 addition ratio is more efficient for welding region and whole welded sample in terms of the supplying uniform superconducting properties as J(c). The obtained results on welded joined bulk superconductor can be beneficial to increase application potential of these superconducting materials in real scale magnetic systems

Magnetic Properties of YBCO Single-Crystal Grown on Y2O3 Layer by a Cold Top-Seeding Method

This study was supported by the Turkish Scientific and Research Council (TUBITAK) research grant (TBAG-107T751) and Karadeniz Technical University research grant (BAP-2008.111.001.8). The authors are grateful to Ms. Kubra Karaoglu for technical assistance.In this work, single-crystal samples 20 mm in diameter were grown by a cold top-seeding method. In order to study the effect of an Y2O3 buffer layer, a compacted precursor was located in a crucible on a buffer layer of freely poured Y2O3 powder. The YBCO bulk samples were carefully prepared in the same chemical composition. In order to examine the homogeneity of the samples, rectangular specimens were cut from a sample. The structural orientation of the specimens was measured by a X-ray diffractrometer (XRD). The microstructure was observed with a Scanning Electron Microscope (SEM). The magnetic properties were measured using a Vibrating Sample Magnetometer (VSM) at 77 K with the applied magnetic field parallel to the c-axis. As a result only (00l) peaks were observed in X-ray diffraction data, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Also the cut samples exhibited very fine Y211 inclusion distributed in the bulk sample observed in SEM micrographs. The critical current density J (c) (A/cm(2)) has been estimated by the extended Bean model. The maximum value of the critical current density at 77 K is 5.2x10(4) A/cm(2) in a self-field. The trapped magnetic field measurements of the samples were performed by using Hall probe scanning device with static field of 0.5 T at 77 K. The single-domain sample exhibits a trapped field of 1140 G at 77 K