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Resumen del póster presentado a la 7th Asian Conference on Applied Superconductivity and Cryogenics celebrado en Capadocia (Turquia) del 23 al 25 de octubre de 2013., In order to see the effect of Fe doping on alignment degree of LFZ grown Bi-2212 superconducting fibers, Bi2Sr2Ca1Cu2−xFexO8+δ (x = 0, 0.01, 0.03, 0.05 and 0.1) nominal composition has been prepared. The fibers obtained through laser floating zone method with a growth rate of 30 mm/h. had a diameter of 1.5-2 mm and up to 15 cm in length. The substitution effect on grain size and alignment degree of the fibers has been investigated by means of SEM and pole diagram, respectively. It has been seen that when the substitution rate reached the highest level, average grain size decreased about one third of the unsubstituted structure. Pole figure diagrams have been clearly showed that increasing doping rate created more aligned grains having ab crystal planes parallel to the growth axis. The most probable reason of this improvement was considered to be increased viscosity of melt region with the effect of doped metallic Fe atoms.

Resumen del póster presentado a la 7th Asian Conference on Applied Superconductivity and Cryogenics celebrado en Capadocia (Turquia) del 23 al 25 de octubre de 2013., In this study, the magnetoresistance of Bi2Sr2Ca0.9Na0.1Cu2O8+δ sample prepared by polymer method for three different sintering temperatures, 850ºC, 860 oC and 870ºC, has been investigated for different values of the applied magnetic field. Broadening of superconducting transition is observed under magnetic field which is explained on the basis of Thermally Activated Flux Flow (TAFF) model. The flux pinning energies are calculated as 0.17 eV for 9 T and 0.02 eV for 0 T. The sample sintered at 850ºC has slightly higher activation energy which is most probably due to the existence of Bi-2201 and Na-content impurities observed at the XRD results.

Resumen del póster presentado a la 7th Asian Conference on Applied Superconductivity and Cryogenics celebrado en Capadocia (Turquia) del 23 al 25 de octubre de 2013., Bi2Sr2Ca1Cu2−xYbxOy (x=0.0, 0.05, 0.1 and 0.25) textured superconductors were prepared by a Laser Floating Zone (LFZ) technique. The X-ray diffraction, DC magnetization and magnetoresistance measurements were studied. All samples consist mainly of the Bi-2212 phase which indicates the performed process is adequate. However, some impurity phases like CaCuO2 were also detected. We have calculated the hole numbers using the relation given by Presland and particle size, Lhkl, using the XRD patterns results.The activation energies, irreversibility fields (Hirr), upper critical fields (Hc2) and coherence lengths at 0K (?(0) ) were calculated from the resistivity versus temperature (R-T) curves, under DC magnetic fields up to 5 T. The thermally activated flux creep model has been studied in order to calculate the flux pinning energies. The results showed that Hc2(0) varied from 132 to 30 T and the flux pinning energies varied from 650 to 400 meV at 0 T, with the content of Yb.

Open access under CC BY-NC-ND license., The introduction of intermetallic semiconductor materials, with higher thermoelectric performances than their metallic counterparts, has resulted in their practical application in thermo-electric modules. These modules can be found as Peltier devices, when used for refrigeration purposes, or Seebeck devices when used for electrical energy generation. Current applications of this kind of material include the environmentally friendly recovery of industrial and automobile waste heat, and in the production of electrical energy in radioisotope thermoelectric generators installed on spacecrafts, or in lighthouses located in isolated regions. At the Department of Materials Science, Universidad de Zaragoza (Spain) much effort has been devoted to optimizing material properties by texturing using the laser floating zone (LFZ) technique. The group is pioneering the application of the LFZ technique on cobaltites to enhance grain orientation and, consequently, thermoelectric properties.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., In this study, the samples with nominal composition of Bi2Sr2Ca1Cu2-xYbxO12+δ, where x =0, 0.05, 0.1 and 0.25, are synthesized by using LFZ (Laser Floating Zone) technique. The effects of different Yb doping on the structure have been investigated by electrical resistance, scanning electron micrographs, XRD, mechanical and dc-magnetization techniques. In order to investigate the magnetic effects of different Yb doping on the structure, the magnetization measurements as a function of the magnetic field up to 10 kOe have been carried out. It has been found that with increasing Yb3+ doping for Cu, the physical and superconducting properties of structure gradually spoils. The Jc values of the samples were calculated by using the Bean’s model. It has been found that the Jc values of the samples significantly change, although TC is approximately the same for all the samples., This work was supported by the Research Fund of Cukurova University, Adana, Turkey, under grant contracts no. FEF2011D21.

The effect of annealing on directionally solidified Bi 2Sr 2Co 1.8O x ceramic rods has been studied for different times up to 1008 h. Microstructure has shown five different phases in the as-grown materials which have been reduced to two major ones after 1008 h thermal treatment, accompanied by an important grain growth. These microstructural changes are reflected on the mechanical properties which are higher than those measured in the as-grown materials in all cases. Moreover, they also produce an important decrease on the resistivity and increase of thermopower, leading to a raise on the power factor on thermally treated samples, about two times, compared to the as-grown samples. © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved., The authors wish to thank the Gobierno de Aragón (Research Groups T12 and T87), the Spanish Ministry of Science and Innovation-FEDER (Project MAT2008-00429), and Universidad de Zaragoza (Project UZ2011-TEC-03) for financial support. The technical contributions of C. Estepa, J.A. Gómez and C. Gallego are also acknowledged. Sh. Rasekh acknowledges a JAE-PreDoc2010 grant from CSIC.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., In this work, we have applied laser floating zone technique, a well -known way of fabricating crystals having highly-aligned dense morphology with improved transport properties, to obtain Bi2Sr2Ca1Cu2-xNixO (x=0, 0.01, 0.03, 0.05 and 0.1) fibers of size 1.8 mm diameter x 12 cm length. Microstructural, magnetic and electrical properties of fibers, grown with optimum growth conditions, were analyzed through scanning electron microscope (SEM), energy dispersive x-ray analysis (EDX), XRD patterns, R-T, I-V, M-T and M-H loops. In SEM/EDX and XRD measurements, it couldn’t be possible to find phases belong to Ni especially for low doping rates. On the other hand, Ni doping caused some negative effects regarding the magnetic properties of fibers.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., The Pb addition effect on the E-I curves obtained in superconducting Bi-2212 textured ceramics has been studied on Bi2-xPbxSr2CaCu2Oy, (x = 0, 0.2, 0.4 and 0.6) materials. They were textured using a laser floating zone melting (LFZ) device with a growth rate of 30 mm/h. The resulting textured cylindrical bars were annealed to develop the Bi-2212 superconducting phase. On these samples, Tc has been determined by electrical resistivity measurements between 77 K and room temperature. Transport Jc values have been calculated from the I-V curves measured at 77K. The microstructure has also been determined and correlated with the measured electrical properties. The influence of Pb doping on the sharpness of the superconducting to normal transition on the E-I curves has been determined, obtaining the sharpest transitions for samples doped with 0.4 Pb.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., Bi2Sr2.1Ca0.9Cu2O8 superconducting ceramics have been prepared by the classical solid state route and textured using the Laser Floating Zone (LFZ) melting technique at 30 mm/h growth speed. The obtained long (more than 12 cm) textured rods were cut into 3 cm long pieces. Silver paint has been applied on each piece to produce the electrical contacts after annealing. All the samples were then annealeded at 860 ºC during 60 h and 800 ºC for 12 h with a final quench to room temperature. Samples characteristics have been determined through electrical resistivity measurements, from 77 K to room temperature, and transport critical current density at 77 K. Based on the phase diagram equilibria, half of the samples were postannealed at 750 ºC for times between 12 and 300 h and the other half at 900 ºC between 5 and 120 minutes. After postannealing, the transport electrical properties have been determined and related with the changes on microstructure.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., In this study, we have reported the physical and magnetic properties of Bi2Sr2CaCu2Ox textured composite materials prepared by a LFZ melting technique at different annealing time (60, 72, 96 and 120 h). SEM images of the samples annealed at 96 and 120 hours indicate very good alignment with the longitudinal rod axis. In all cases, X-ray diffraction patterns show that the Bi-2212 phase is the major one. The magnetization measurements have been carried out as a function of the magnetic field up to 9 kOe. Jc values of the samples were calculated by using the Bean’s model. The results indicate that the different annealing time has no significant effects on the Tc values but, significant change on the critical current values of samples, Jc, has been obtained for sample annealed at 96 hours. We also found that the maximum critical density of Jc is 5.5x105 A/cm2 at 10K for the 96 hours annealed sample.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., The development of practical applications of high temperature superconductors requires not only the knowledge of their electrical properties, but their behaviour under different environments. Bulk Bi-2212 superconductors have demonstrated that they are suitable for many applications when they are properly processed, for example trough the laser floating zone technique. The Bi-2212 bulk materials textured by this technique have very interesting electrical properties that allow developing current leads and fault current limiters. One of the main advantages of this method is that samples can be rapidly grown due to the large thermal gradients present at the solid-liquid interface. On the other hand, for any practical application, it is necessary to take into account their reactivity to moisture and carbon dioxide, which leads to their chemical degradation as: Bi2Sr2CaCu2O8 + 3H2O -----> 2Sr(OH)2 + Ca(OH)2 + CuO + CuBi2O4 Sr(OH)2 + CO2 -----> SrCO3 + H2O Ca(OH)2 + CO2 -----> CaCO3 + H2O In this work, the environmental (water and saturated carbon dioxide water) susceptibility of Bi-2212 thin rods grown by laser floating zone method has been measured by means of electrical properties variation (critical current density and resistivity). Although the electrical properties did not change considerably it has been found a higher influence on the mechanical ones. It has been also found that the special microstructure developed in the growth process is responsible for this behaviour. On the other hand, this influence must be considered in practical applications in order to maintain the mechanical integrity of the system.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., In this study, Bi2Sr2Ca1-xCexCu2O8+y samples with x=0.0; 0.01; 0.05; 0.1 and 0.25 were prepared by solid-state reaction method. These powders were used as precursors to fabricate long textured cylindrical bars through a laser floating zone melting method (LFZ). The electrical, structural and magnetic properties of the samples have been characterized by X-ray diffraction (XRD), electrical resistance, scanning electron microscopy (SEM) and Vibrating Sample Magnetometer (VSM). The critical current density, Jc, was calculated by means of well-known Bean’s Critical State Model.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., In this paper, we have produced the highly-aligned Bi2Sr2Ca1Cu2-xFexO superconducting fibers by laser floating zone (LFZ) technique containing Nd:YAG laser beam with 1064 nm wavelength as a continuous power source for x = 0, 0.01, 0.03, 0.05 and 0.1 doping rates. The effects of iron doping on the grain alignment and superconducting properties of fibers were investigated by the detailed scanning electron microscopy and energy dispersive spectroscopy microanalysis from both the as-grown and annealed rods with 1.5-2 mm in diameter and up to 15 cm in length. In addition to these investigations phase studies, electrical and magnetic measurements were realized through XRD, R-T, M-T and M-H loops. At the same time, magnetization of fibers was studied with the magnetic fields applied from different axes. With the same growth conditions, increasing doping rate degraded the texturing level and also magnetic properties of samples.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., The development of commercial applications based on high temperature superconductors requires the use of texturing techniques in order to obtain the properties that are needed for technological applications. The Bi2Sr2CaCu2O8+δ (Bi-2212) superconductor has demonstrated its suitability for many applications when it is properly processed. A texturing technique for Bi-2212 bulk materials is the laser floating zone (LFZ) method. The superconducting materials textured by this technique, have very well aligned crystals, with their a-b planes parallel to the current flow. These textured bulk materials have very interesting properties that have been used to design current leads or fault current limiters which contribute to improve quality, reliability and flexibility of the electric grid. However, the low slope of the superconducting to normal transition on the electrical current curve, E-I, imposes limitations for their application as fault current limiters. A solution to overcome this problem is based on the cationic substitution, which could introduce effective flux pinning centres and increase the slope of the E-I curves. Previous works, on the Bi substitution by Pb has demonstrated that the slope of the I-V curves can be increased considerably. On the other hand, small Ag additions have shown to be very useful in order to improve considerably the mechanical behaviour of these totally melt-processed materials. In this work we analyse the influence of simultaneous additions (Pb and Ag) on the microstructure and the superconducting properties of LFZ textured (Bi2-xPbx)Sr2CaCu2O8+δ bars, with x = 0 and 0.4 and small (0,1 and 3% wt) Ag additions.

Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Española de Cerámica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012., The development of practical applications of high temperature superconductors requires not only the knowledge of their electrical properties, but their behaviour under different environments. Bulk Bi‐2212 superconductors have demonstrated that they are suitable for many applications when they are properly processed, for example trough the laser floating zone technique. The Bi‐2212 bulk materials textured by this technique have very interesting electrical properties that allow developing current leads and fault current limiters. One of the main advantages of this method is that samples can be rapidly grown due to the large thermal gradients present at the solid‐liquid interface. On the other hand, for any practical application, it is necessary to take into account their reactivity to moisture and carbon dioxide, which leads to their chemical degradation. In this work, the environmental (water and saturated carbon dioxide water) susceptibility of Bi‐2212 thin rods grown by laser floating zone method has been measured by means of electrical properties variation (critical current density and resistivity). Although the electrical properties did not change considerably it has been found a higher influence on the mechanical ones. It has been also found that the special microstructure developed in the growth process is responsible for this behaviour. On the other hand, this influence must be considered in practical applications in order to maintain the mechanical integrity of the system.

Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Española de Cerámica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012., Bi2Sr2Co1.8Ox/Ag composites with small amounts of Ag have been synthesized by a sol–gel via nitrates reaction and directionally grown from the melt. Some of the obtained samples were annealed in order to obtain the thermoelectric phase as the major one. As‐grown and annealed samples were microstructurally characterized to determine the phases distribution and alignment. Moreover, thermoelectric and mechanical characteristics of annealed samples were determined by the four‐probe technique and by three point flexural strength tests, respectively. Scanning electron microscopy revealed that Ag particles appear dispersed among well oriented ceramic grains with large size, providing a plastic flow region which increases the flexural strength for the optimally Ag added samples (1 wt.%). The composites electrical resistivity is lower than that of pure Bi2Sr2Co1.8Ox while Ag addition does not significantly affect thermopower values. The resistivity reduction leads to power factor improvements of ≅50%, compared with pure samples, for Ag additions of 1 wt.% Ag.

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012., Bi-2212+3%Ag superconducting ceramics were grown using the electrically assisted laser floating zone (EALFZ) technique. The main goal was improving the superconducting properties by applying an electrical current through the sample during the solidification process. The effect of a 100mA current intensity, in two configurations, one connecting the feed to the positive pole and the seed to the negative one, and viceversa, were studied. Once the best polarity was determined, the bars were grown with different current intensities (100-300mA) and compared with the ones grown without current. The resulting textured cylindrical bars were annealed in order to obtain the superconducting phases, followed by electrical characterization. Microstructure was analysed and correlated with the electrical properties as well as the applied current intensity in the growth process. The influence of current intensity on the sharpness of the superconducting to normal transition on the E-I curves has been determined.

Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Española de Cerámica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012., Bi1.6Pb0.4Sr2Co1.8Oy/Ag composites with small amounts of Ag (0, 1 and 3wt.%) have been synthesized by a sol‐gel via nitrates reaction and directionally grown from the melt. As‐grown samples were microstructurally characterized to determine the phases distribution and alignment. Moreover, thermoelectric characteristics were determined by the four‐probe technique. Scanning electron microscopy revealed that Ag particles appear dispersed among well oriented ceramic grains with large size. The composites electrical resistivity is lower than that of pure Bi1.6Pb0.4Sr2Co1.8Oy. The resistivity reduction leads to power factor improvements higher than 50%, compared with pure samples, for Ag additions of 3wt.%Ag.

Trabajo presentado al XI Congreso Nacional de Materiales celebrado en Zaragoza del 23 al 25 de junio de 2010., En este trabajo se muestran las mejoras introducidas sobre las propiedades termoeléctricas de muestras masivas con composición Bi2Ca2Co1.7Ox y Bi2Sr2Co1.8Ox, cuando son adecuadamente texturadas mediante un proceso de solidificación direccional asistido por láser. La composición y microestructura de las muestras han sido estudiadas mediante difracción de rayos X y microscopia electrónica de barrido. Las propiedades termoeléctricas se han medido entre 50 y 650 ºC mediante la determinación simultánea de la resistividad eléctrica y del poder termoeléctrico. En todos los casos, las muestras texturadas presentan apreciables mejoras en los valores del factor de potencia cuando se comparan con cerámicas sinterizadas de forma convencional mediante técnicas de estado sólido., Los autores agradecen la ayuda del Gobierno de Aragón (grupos de investigación T12 y T74, proyecto PI154/08) y al Ministerio de Ciencia e Innovación (proyecto MAT2008-00429).

substitution and subsequent grain orientation. This can be performed preparing the ceramics by a polymer solution method, using Pb partially substituting Bi, and texturing by directionally growing from the melt. In this work, Bi2-xPbxCa2Co1.7Oy (x = 0.0, 0.2, 0.4 and 0.6) ceramics, prepared by a polymer solution method, have been directionally grown, with the Laser Floating Zone (LFZ) technique, at 30 mm/h. In all the cases, the microstructure shows alternated layers with small CoO inclusions. It has been found a very important decrease on the resistivity and, at the same time, on the thermopower. However, the power factor values are improved with Pb addition, reaching power factor values, for samples with 0.4 Pb substitution, as high as two times the values obtained for undoped ones.

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[EN] In this work, superconducting samples of (Bi1.6Pb0.4)Sr2CaCu2O8+δ with Ag additions have been studied. (Bi1.6Pb0.4)Sr2CaCu2O8+δ + x wt.% Ag (with x = 0, 1 and 3) powders were synthesized using a sol-gel method. The obtained powders were used as precursors to fabricate long textured cylindrical bars through a floating zone melting method. A drastic change on the microstructure has been found when comparing with undoped Bi2Sr2CaCu2O8+δ samples. The results showed that electrical resistivity at room temperature, critical current as well as flexural strength are improved when Ag is added to these Pb doped samples, while critical temperature does not change. On the other hand, it has been found that samples with composition (Bi1.6Pb0.4)Sr2CaCu2O8+δ + Ag shown E-I curves with very high sharpness values on the zone of the superconducting to normal transition, reaching n-values (E∼In) as high as 45 at 65K., [ES] Se han preparado polvos cerámicos de composición (Bi1.6Pb0.4)Sr2CaCu2O8+δ + x % Ag en peso (con x = 0, 1 y 3) mediante un proceso sol-gel. Estos polvos se han utilizado para fabricar precursores que se texturaron por medio del método de fusión zonal flotante. Se ha encontrado un gran cambio en la microestructura cuando se compara con muestras de composición pura Bi2Sr2CaCu2O8+δ. Tanto la resistividad eléctrica a temperatura ambiente, como la corriente crítica, así como la resistencia a flexión se mejoran cuando la Ag se adiciona a estas muestras dopadas con Pb, mientras que no se observa cambio en la temperatura crítica. Por otra parte, se ha encontrado que las muestras de composición (Bi1.6Pb0.4)Sr2CaCu2O8+δ + Ag presentan una gran pendiente de la curva E-I en la zona de transición entre el estado superconductor y el estado normal. Con estas composiciones, se han encontrado valores de n (E∼In) de hasta 45 a 65K., The authors are indebted the Spanish Ministry for Education and Science (MAT 2005-06279-C03-01) and to the Aragón Regional Government (Consolidated Research Groups E03 and T12) for financial support.