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Ac loss and ramp up related heating effects in superconducting mgb(2) coils
(Ieee-Inst Electrical Electronics Engineers Inc, 2020) Yetiş, Hakan; Akdoğan, Mustafa; Karaboğa, Fırat; Avcı, Doğan; Belenli, İbrahim
Superconducting coils modeled by using single core MgB2 wires having copper or iron or both in the cross section as sheath materials have been examined numerically by using the magnetic field formulation and heat transfer modules of COMSOL Multiphysics software. Heating effects due to the core ac losses and skin effects in MgB2 coils are revealed for alternating currents in a liquid helium environment. Temperature changes, magnetic flux density profiles, core ac losses for each coil are obtained in one full cycle of applied alternating current. The effect of copper layer thickness on core ac loss behavior of MgB2/Cu coil and transport losses in MgB2/Cu and MgB2/Fe coils as a function of current ramp rate are investigated for an applied direct current up to 300 A.
AC loss characteristics of CORC((R))cable with a Cu former
(Iop Publishing Ltd, 2017) Terzioglu, Rıfkı; Vojenciak, Michal; Sheng, Jie; Gömöry, Fedor; Çavuş, Türker Fedai; Belenli, İbrahim
High-temperature superconductors from the REBCO (RE = rare earth) family have attained industrial production and their performance is continuously being enhanced. However, cabling technology for high-current (kA range) cables for magnet technology is still challenging and there are only few cable concepts available (CORC (R), Roebel cable, twisted stack cable). Each of them exhibits different characteristics. In this paper we experimentally investigate CORC (R) cable produced in-house utilizing a copper tube former. Such a former offers a central cooling channel for partial or complete cable cooling by forced flow of coolant. We focus mainly on AC loss due to transporting AC current, an external applied AC magnetic field and their simultaneous action. In the case of transporting AC current we found indications that a large part of the total loss has its origin in eddy currents due to an axial magnetic field. For the investigation of magnetization AC loss, we prepared several samples with different configurations. In this case we found direct evidence for increasing AC loss due to losses in the metallic former. However, we also found that at low field amplitudes the magnetization AC loss of the complete cable is lower than the loss in the bare former. This is caused by shielding of the magnetic field by a superconductor, which was also confirmed by numerical simulations.
Batı Karadeniz bölgesindeki dalga enerjisi potansiyelinin araştırılması
(2006) Uygur, İlyas; Demirci, Recep; Saruhan, Hamit; Özkan, Arif; Belenli, İbrahim
Çevreye zarar vermeyen doğal, temiz ve sürekli yenilenebilir enerji türlerinin başlıcaları, rüzgar, güneş, biyolojik, su ve dalga enerjisidir. Dalga enerjisi, ilk yatırım ve bakım giderlerinden başka masrafı olmayan, girdi bedeli gerektirmeyen, doğaya her hangi bir kirletici bırakmayan, ucuz, temiz, çevreci ve büyük potansiyele sahip bir enerji kaynağıdır. Üç tarafı denizlerle çevrili Türkiye için de dalga enerjisi, enerji sıkıntısı çektiğimiz şu günlerde ve ileriki yıllarda bir çözüm olabilecek durumdadır. Bu bağlamda Batı Karadeniz (Akçakoca) bölgesinde beş yıllık gözlemsel çalışmalar yapılmış ve bölgenin dalga enerji potansiyeli hesaplanmıştır. Meteoroloji verilerinin incelenmesi neticesinde bölgedeki dalga enerjisi güç potansiyeli, mevcut teknolojik sistemler için yetersiz olarak gözükmektedir. Gelişen teknolojiyle birlikte üretilen yeni enerji dönüştürücülerinin de gelişeceği gözünde bulundurularak, yetersiz olarak tespit edilen dalga enerjisi potansiyeli daha verimli bir şekilde değerlendirilebilir. Bu çalışma bundan sonraki araştırmalar için bir temel teşkil edebilecektir.
Corrigendum to “The effect of Nb substitution on magnetic properties of BaFe12O19 nanohexaferrites” [Ceram. Int. 45 (2019) 1691–1697](S027288421832844X)(10.1016/j.ceramint.2018.10.048)
(Elsevier Ltd, 2019) Almessiere, Munirah Abdullah; Slimani, Yassine; Tashkandi ,Na Tashkandi; Baykal, Abdulhadi; Saraç, Mehmet Fahri; Belenli, İbrahim
The authors regret that in the published version of this article two additional affiliation addresses were missing for the author A.V. Trukhanov. The affiliation additional addresses are: National University of Science and Technology MISiS, 119049, Moscow, Leninsky Prospekt, 4, Russia South Ural State University, 454080, Chelyabinsk, Lenin Prospect, 76, Russia The authors would like to apologise for any inconvenience caused. © 2018 Elsevier Ltd and Techna Group S.r.l.
Design, fabrication, and testing of MgB2/Fe racetrack coils
(Ieee-Inst Electrical Electronics Engineers Inc, 2018) Karaboğa, Fırat; Yetiş, Hakan; Akdoğan, Mustafa; Gajda, Daniel; Belenli, İbrahim
We fabricated four superconducting racetrack coils wound by bare in situ MgB2/Fe mono and multifilamentary wires produced in our laboratory by using the wind-and-react method. Transport measurements in self-field were performed in a liquid helium dewar. The magnetic field flux density B = 25 mT for I = 92 A was measured to verify how the current flowed inside the coil for one of the coils by means of a cryogenic axial Hall sensor placed into the central bore region of the coil. The coil with 36 turns wound by mono MgB2/Fe wire of l = 24 m has a highest current-carrying capacity of more than 150 A at T = 4.2 K and self-field among the coils. The coils fabricated by multifilamentary wires have relatively low engineering critical current values of I-ce = 67 A for 18 + 1 and I-ce = 57 A for 4 + 5 superconducting/copper filament wires at T = 4.2 K in self-field. Our results form essential contribution toward determination of the possible use of low-cost MgB2/Fe wires in low-field superconductor coil applications.
Diffusion coefficient, activation energy and the effect of Ag-doping on some physical properties of silver doped Bi1.8Pb0.4Ca2.2Sr2Cu3Ox
(Elsevier Science Bv, 2010) Akdoğan, Mustafa; Terzioğlu, Cabir; Varilci, Ahmet; Belenli, İbrahim
The aim of the present study is to investigate the effect of diffusion-doped silver on some physical properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Ox superconducting samples and to calculate the diffusion coefficient and the activation energy of silver. The present work consists of three parts: (a) optimization of annealing temperature, (b) the effect of Ag diffusion-doped on microstructure and superconducting properties of Bi(Pb)CaSrCuO, and (c) calculation of diffusion coefficient of silver. First, to investigate the optimum annealing temperature we prepared Bi1.8Pb0.4Ca2.2Sr2Cu3Ox ceramic superconductors annealed at 830, 835, 840, 845, and 850 degrees C using the solid state reaction method. The investigations consist of XRD, SEM, dc resistivity, and transport critical current density measurements. The highest T-c and J(c) values were observed for the sample annealed at 840 degrees C for 48 h (B840). Large grain size, denser surface, and high volume fraction of the high-T-c phase were obtained for the sample B840. The diffusion doping of Bi1.8Pb0.4Ca2.2Sr2Cu3Ox by silver increased the critical current density from 123 to 696 A/cm(2) and the transition critical temperature by about 3 K compared with the undoped sample. Ag-doping increased the amount of high-T-c phase and improved the surface morphology. It also caused an increase of the lattice parameter c by an amount of 0.15%. The temperature dependence of the silver diffusion coefficient in the range 600-800 degrees C is described by D=2.9 x 10(-4)exp(-1.05 eV/k(B)T). Possible reasons for the observed improvement in the structural and superconducting properties of the samples due to silver diffusion are discussed. (C) 2010 Elsevier B.V. All rights reserved.
The effect of Au diffusion on some physical properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors
(Elsevier Science Sa, 2009) Terzioğlu, Cabir; Öztürk, Özgür; Belenli, İbrahim
We have investigated the effect of the gold diffusion on the crystal structure and superconducting properties of Bi-2223 superconducting samples employing X-ray diffraction (XRD), scanning electron microscopy (SEM), critical transition temperature, critical current density, and room temperature resistivity measurements. Doping of Bi-2223 was carried out by means of gold diffusion from an evaporated gold film on pellets during sintering. XRD patterns and SEM micrographs are used to obtain information about Bi-2223 phase ratio, lattice parameters and grain size, respectively. Au doping of the samples increased the critical transition temperature and the critical current density from 100 +/- 0.2 to 104 +/- 0.2 K and from 40 to 125 A cm(-2), in comparison with those of undoped samples. The gold diffusion in Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy has been studied over the temperature range of 500-830 degrees C using the technique of successive removal of thin layers and measurement of the sample's conductivity at room temperature. The temperature dependence of the Au diffusion coefficient in the range of 500-830 degrees C was described by the relation D = 5 x 10(-4) exp (-1.09 eV/kBT). The possible reasons for the observed improvements in microstructure and superconducting properties due to Au diffusion were discussed. (c) 2008 Elsevier B.V. All rights reserved.
Effect of bimetallic (Ca, Mg) substitution on magneto-optical properties of NiFe2O4 nanoparticles
(Elsevier Sci Ltd, 2019) Slimani, Yassine; Almessiere, M. A.; Nawaz, M.; Baykal, A.; Akhtar, S.; Ercan, I; Belenli, İbrahim
Nanoparticles (NPs) of calcium and magnesium co-substituted nickel ferrite with the chemical composition CaxMgxNi1-2xFe2O4 (0.00 <= x <= 0.05) NPs were prepared hydrothermally. The (Ca, Mg) co-substitution effect on morphological, structural, optical and magnetic properties of NiFe2O4 NPs was analyzed via FT-IR, XRD, TEM, SEM, DRS and VSM techniques. The magnetization of CaxMgxNi1-2xFe2O4 (0.00 <= x <= 0.05) NPs were examined and analyzed at room temperature (300 K; RT) and low temperature (10 K). The specific magnetic parameters such as saturation magnetization M-s, remanence M-r, coercivity H-c, squareness ratio (SQR = M-r/M-s) and magnetic moment nB of Ni1-2xMgxCaxFe2O4 (0.00 <= x <= 0.05) NPs were determined and evaluated. The M (H) curves exhibit superparamagnetic behavior at RT and ferrimagnetic nature at 10 K. The substitution significantly changes the magnetizations and coercivity data. An increase in the M-s, M-r, H-c, and nB values was observed in substituted products compared to pristine one. The highest values were obtained for x = 0.05 product. The SQR values are found to be below than 0.5, which can be attributed to surface spin disorder effects. The obtained magnetic results are primarily derived from the substitution with Mg and Ca that will strengthen the super exchange interactions.
Effect of cooling rates on bare bulk and silver wrapped pellets of Bi-2223 superconductor
(Elsevier, 2006) Terzioğlu, Cabir; Öztürk, Özgür; Kılıç, Ahmet; Gencer, Ali; Belenli, İbrahim
We have examined the effect of cooling rates on oxygen content of Bi-2223 phase samples with and without silver sheating. Two sets of samples with and without silver sheating were annealed under identical conditions and cooled with rates of 10 degrees C/h, 25 degrees C/h, 50 degrees C/h, 75 degrees C/h, and 100 degrees C/h. XRD examination of the samples showed that a high percentage of Bi-2223 was obtained. Microstructure examinations were performed by scanning electron microscopy. Resistive and magnetic transitions of the samples were studied. All the reported data were discussed and related.
Effect of different-sized h-BN nano-particles on some properties of MgB2 superconductors
(Springer, 2016) Karaboğa, Fırat; Yetiş, Hakan; Öz, Muhammed; Belenli, İbrahim
The present study reports the effect of hexagonal boron nitride (h-BN) doping on the superconducting properties of bulk MgB2 samples. Structural, electrical and magnetic properties of 3 wt% h-BN doped MgB2 samples are studied in terms of three different sized h-BN nanoparticles. The results show that h-BN doping has no significant change on critical transition temperature (+/- 0.5 K deviation), but decreases the magnetic J (c) with increasing the h-BN particle size. Among the doped samples, a highest J (c) (T = 10 K) value of 1.8 x 10(4) A/cm(2) is achieved for the sample doped with the smallest sized h-BN at zero external magnetic field but it is still lower than the 2.5 x 10(4) A/cm(2) obtained for the un-doped sample. In the scope of this study, it is investigated whether or not the nano-sized h-BN particle is a possible candidate to improve the pinning properties of the MgB2 sample and we suggest that particle size is very important parameter in h-BN doping into MgB2.
The effect of Fe diffusion on some physical and superconducting properties of MgB2
(Springer, 2017) Ülgen, Asaf Tolga; Belenli, İbrahim
The iron (Fe) diffusion in superconducting MgB2 bulk samples has been studied over the temperature range of 650-900 degrees C for 1 h. Fe coating on bulk polycrstalline superconducting MgB2 samples was performed in two ways, i.e., on pressed pellets without sintering (set(2)) and on pressed and sintered pellets (set(1)). For both sets, a 50 mu m thick Fe layer was coated on MgB2 by evaporation in vacuum. Effects of Fe diffusion on the crystal structure and superconducting properties of MgB2 have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and resistivity measurements. Fe diffusion coefficients were determined from lattice parameter c and room temperature resistivity values. The temperature dependence of the Fe diffusion coefficient in this temperature range is described by the Arrhenius relation. It has been found that the Fe diffusion coefficient increases with increasing sintering temperature, as expected. The plausible explanations for the observed improvement in microstructure and superconducting properties of the samples due to Fe diffusion are discussed.
Effect of Gd addition on the activation energies of Bi-2223 superconductor
(Elsevier Science Bv, 2011) Erdem, M.; Öztürk, Özgür; Yücel, E.; Altıntaş, Sevgi Polat; Varilci, Ahmet; Terzioğlu, Cabir; Belenli, İbrahim
We have investigated the effect of addition of Gd in Bi1.8Pb0.35Sr1.9Ca2.1Cu3GdxOy superconductor with x=0, 0.1, 0.2, 0.3, 0.4 and 0.5. The samples were prepared using the standard solid-state reaction method. The activation energies, irreversibility fields (H-irr), upper critical fields (H-c2) and coherence lengths at 0 K (xi(0)) were calculated from the resistivity versus temperature (R-T) curves under DC magnetic fields up to 7 T. The superconducting transition temperature, T-c, and activation energy, U-0, were found to decrease with increase in Gd concentration and with increase in applied magnetic field. The offset transition temperature of the pure (Gd00) sample without applied magnetic field is 108 K, whereas for Gd05 sample, the offset transition temperature drops to 5 K with 7 T applied magnetic field. The activation energy of the Gd00 sample without applied magnetic field is 34,980 K, and for Gd05 sample with 7 T applied field it is 98 K. H-irr and H-c2 values also decrease with increase in Gd addition. The possible reasons for the observed degradation in microstructural and superconducting properties due to Gd addition were discussed. (C) 2010 Elsevier B.V. All rights reserved.
The effect of Nb substitution on magnetic properties of BaFe12O19 nanohexaferrites
(Elsevier Ltd, 2019) Almessiere, Munirah Abdullah; Slimani, Yassine; Tashkandi ,Na Tashkandi; Baykal, Abdulhadi; Saraç, Mehmet Fahri; Belenli, İbrahim
Microstructural and magnetic properties of BaFe12-xNbxO19 (0.0 ? x ? 0.1) nanohexaferrites (NHFs) have been investigated intensively in this work. The Ba NHFs are synthesized through sol-gel auto-combustion route. The formation of single phase Ba NHFs, in different samples are confirmed by XRD powder patterns, scanning electron microscopy and Fourier Transform Infrared spectroscopy. The magnetic properties of BaFe12-xNbxO19 (0.0 ? x ? 0.1) NHFs were performed at room and low temperatures and discussed in detail. The analysis of hysteresis loops divulged that the different products display hard ferromagnetic behavior at different temperatures. The deduced values of saturation magnetization (Ms), remanence (Mr), magneton number (nB) and magneto crystalline anisotropy constant (Keff) are reduced for lower Nb content and then increased with further increasing the Nb content, reaching a maximum values for BaFe11.9Nb0.1O19 (x = 0.1) nanohexaferrite. The coercivity (Hc) and intrinsic coercivity (Hci) are diminished for lower x and are comparable to that of pristine one for higher x. The squareness ratio (Mr/Ms) are fluctuating between 0.50 and 0.55, implying the uniaxial anisotropy for different BaFe12-xNbxO19 nanohexaferrite. © 2018 Elsevier Ltd and Techna Group S.r.l.
Effect of the initial filling density on the critical current of in-situ Fe/MgB2 wires
(Elsevier Science Sa, 2015) Akdoğan, Mustafa; Yetiş, Hakan; Gajda, Daniel; Karaboğa, Fırat; Ülgen, Asaf Tolga; Demirtürk, Emine; Belenli, İbrahim
We report a comparative study on the fabrication of in-situ monofilamentary superconducting Fe sheathed MgB2 wires as a function of the initial tube filling density. The wire samples are fabricated by means of a standard Powder-in-Tube (PIT) method with two different initial powder filling densities. Transport measurements are applied under high magnetic fields, of up to 10 T, obtained in a Bitter magnet. We find that increasing the initial filling density improved the critical current of the Fe/MgB2 wires, and a high I-c (4.2 K) = 140 A at B = 5 T is achieved. (C) 2015 Elsevier B.V. All rights reserved.
The effect of the number of Ag layers on some physical properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Ox
(Springer, 2012) Akdoğan, Mustafa; Erdem, M.; Terzioğlu, Cabir; Belenli, İbrahim
Bi1.8Pb0.4Ca2.2Sr2Cu3Ox/Ag multilayered samples with 2, 4 and 8 layers are prepared by powder in tube (PIT) method and the effect of multilayering with Ag on the superconducting and the microstructural properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Ox is studied. The investigations consist of XRD, SEM, EDS, magnetoresistivity, and I-V measurements. In the magnetoresistivity measurements, magnetic fields up to 0.5 T are applied both parallel and perpendicular to the current flow direction. The superconducting and microstructure properties of the samples are enhanced as the number of Ag layers are increased. The samples are composed of a highly oriented Bi-2223 phase in the regions near the Ag layers. The formation of the dense oriented structure is near the interface between oxide and the Ag layer. T-c and J(c) values are enhanced from 107 to 109 K and from 240 to 600 A/cm(2) by increasing the number of Ag layers, respectively. The results suggest that Ag plays an important role in the improvement of superconducting properties. The possible mechanisms of the enhancement of superconducting properties due to Ag layering are discussed.
Effects of mg-coating and boron type on electromechanical properties of IMD MgB2/Fe wires
(Springer, 2021) Avcı, Doğan; Yetiş, Hakan; Karaboğa, Fırat; Akdoğan, Mustafa; Belenli, İbrahim
In this study, mechanical and electrical characterization measurements were performed on non-bent and gradually bent IMD MgB2/Fe superconducting round wires having 0.81 mm outer diameter. Four straight IMD wires were successively bent to 150 mm, 125 mm, and 100 mm bending diameters and characterized after each bending step. IMD wires were produced using two types of boron powders (PVZ Nano Boron, purity > 98.5%, particle sizes < 250 nm, and PVZ boron, purity of 95-97%, particle sizes < 1 mu m) by filling them into Mg-coated and uncoated iron tubes. The coated Mg was considered as an extra source of Mg that diffuses into the Mg + 2B core without causing any porosity during the reaction. We have investigated the effect of Mg coating on the transport and electromechanical properties of the wires and found that the Mg coating process improves the J(ce) before and after bending. Also, our results have revealed that crack formation in core regions of mono filament bent IMD wires depends on the type of boron, since the use of nano-sized boron significantly increases the hardness of the MgB2 core.
Electrical conductivity of the ionic conductor tetragonal (Bi 2O3)1-x(Eu2O3) x
(Associacao Brasileira de Ceramica, 2011) Yılmaz, Serdar; Türkoğlu, Orhan; Arı, Musab; Belenli, İbrahim
Electrical conductivity of tetragonal ?-phase (Bi2O 3)1-x(Eu2O3)x (0.01 ? × ? 0.10 %mol) ceramic systems were investigated. The temperature and doping concentration dependences of the electrical conductivity were studied by four-point probe technique. The electrical conductivity increases with the increasing doping concentration and temperature. The highest value of the electrical conductivity is 0.013 ?-1cm-1 (x = 0.05, 750 °C) for the ?-phase at 670 oC and 0.57 ?-1cm -1 (x=0.05, 800 °C) in binary systems at 690 °C. The phase transition which manifests itself by the jump in the conductivity curves was seen and verified by differential thermal analysis measurements. The activation energies of the samples were found to be about 0.71-1.57 eV.
Fabrication and magnetoresistivit of ex-situ processed MgB2/Fe monofilament tapes without any intermediate annealing
(Springer, 2011) Yücel, E.; Terzioğlu, Cabir; Varilci, Ahmet; Belenli, İbrahim
We have fabricated MgB2/Fe monofilament wires and tapes by a powder-in tube (PIT) technique, using an ex-situ process without any intermediate annealing. MgB2/Fe monofilament tapes were annealed at 650-1,050A degrees C for 60 min and 950A degrees C for 30-240 min. We have investigated the effect of annealing temperatures and times on the formation of MgB2 phase, activation energy, temperature dependence of irreversibility field H (irr)(T) and upper critical field H (c2)(T), transition temperature (T (c)), lattice parameters (a and c), full width at half maximum, crystallinity, resistivity, residual resistivity ratio, active cross-sectional area fraction and critical current densities. We observed that the activation energies of the MgB2/Fe monofilament samples increased with increasing annealing temperature up to 950A degrees C and with increasing annealing time up to 60 min while it decreased with increasing magnetic field. For the MgB2/Fe monofilament tape, the slope of the H (c2)-T and H (irr)-T curves decreased with increasing annealing temperature from 850 to 950A degrees C as well as with increasing annealing time from 30 to 60 min. The transport and microstructure investigations show that T (c), J (c) and microstructure properties are remarkably enhanced with increasing annealing temperature. The highest value of critical current density is obtained for the sample annealed at 950A degrees C for 60 min. The J (c) and T (c) (offset) values of the sample annealed at 950A degrees C for 60 min were found to be 260.43 A/cm(2) at 20 and 38.1 K, respectively.
Fabrication and superconducting properties of ex-situ processed MgB2/Fe monofilament tapes without any intermediate annealing
(Elsevier, 2011) Yücel, E.; Terzioğlu, Cabir; Varilci, Ahmet; Gencer, A.; Belenli, İbrahim
We have investigated the effect of annealing time and temperature on the formation of the MgB2 phase, transition temperature (T-c), lattice parameters (a and c), full width at half maximum (FWHM) of the X-ray diffraction, crystallinity, resistivity (rho), residual resistivity ratio (RRR), active cross-sectional area fraction (A(F)), and critical current densities (J(c)) of MgB2/Fe monofilament tapes fabricated using an ex-situ powder-in-tube (PIT) method without any intermediate annealing. To obtain the optimum annealing temperature, MgB2/Fe monofilament tapes were annealed at 650, 750, 850, 950, and 1050 degrees C for 60 minutes. From these investigations, the optimum annealing temperature was found to be 950 degrees C. Then, to obtain the optimum annealing time, the samples were annealed at 950 degrees C for 15, 30, 60, 120, 180, and 240 minutes. The samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), optical microscope, critical transition temperature (T-c), and critical current density (J(c)) measurements. The transport and microstructure investigations show that T-c, J(c), and the microstructure properties are remarkably enhanced with increasing annealing temperature up to 950 degrees C. The highest value of the critical current density was obtained after annealing at 950 degrees C for 60 minutes. The J(c) and T-c(offset) c values of the sample annealed at 950 degrees C for 60 minutes were found to be 260.43 A/cm(2) at 20 K and 38.1 K, respectively.
Fabrication and transport critical current densities of MgB2/Fe/Cu multifilament tapes without any intermediate annealing
(Polish Acad Sciences Inst Physics, 2012) Yücel, Ersin; Terzioğlu, Cabir; Varilci, Ahmet; Gencer, Ali; Belenli, İbrahim
We have fabricated superconducting 6 and 7 filaments MgB2/Fe/Cu tapes by ex situ powder-in-tube method using Cu-sheath without any intermediate annealing. Properties of two different multicore MgB2/Fe/Cu tapes annealed at 900 degrees C for 2 h in high purity argon gas atmosphere were compared. The samples were characterized using scanning electron microscope, X-ray diffraction, electron dispersive spectroscopy, optical microscopy, critical transition temperature, transport critical current density, and magnetic measurements. Transport critical current densities of the 6 and 7 filaments tapes were found to be 450 A/cm(2) and 190 A/cm(2) at 20 K, respectively. From X-ray diffraction measurements, lattice parameters a and c were determined. From dc resistivity measurements, the connectivity between grains was investigated by using Rowell's connectivity analysis.

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