Pure Y123 Research Articles

Investigation of structural and Magnetic properties of (Nb) Substituted YBCO-system

In this study, we report the synthesis and characterization of YBa2Cu3O7-δ (YBCO) high temperature superconductor prepared by solid state method and doped with Nb in different weight percentages, 0, 0.01, 0.02 and 0.05 wt%. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We evaluated the effects of Nb doping on the normal state resistivity (ρ), superconducting transition temperature (Tc), scanning electron microscope (SEM. The critical current densities, JC as a function of temperature have been calculated using the critical state model from the hysteresis loops up to 1T at temperature range of 10K to 60K. Magnetic flux pinning, FP of samples was calculated by using Lorentz force. XRD analysis show a shorter c axis parameter and higher orthoromthcity than the pure Y-123 and other Nb doped samples. It was also found from critical current density and magnetic flux pinning force measurement the 0.01 wt% Nb substation for Y on YBCO superconductors improve the critical current density and flux pinning force.

The effect of partial Nb doping on magnetic and electrical behavior of Y-123 superconductors with Nano CuO

: We have investigated the effect of Niobium and Nano CuO (40 nm) dopingY1-xNbxBa2Cu3O7-∂ compounds with 0.00 ≤ x ≤ 0.05 wt. %, prepared by the conventional solid-state method by means of XRD, SEM, R(T) and magnetic loops (M-H) measurements. The critical current densities, Jc as a function of temperature have been calculated using the critical state model from the hysteresis loops up to 1 kG at the temperature range of 10-60 K. Magnetic flux pinning, Fp of samples was calculated by using Lorentz force. The temperature dependence of the electrical resistivity measurement curves indicated that the sample with x=0.01 wt.% has a high transition temperature, Tc. XRD analysis shows a shorter c axis lattice parameter and higher orthoromthcity than the pure Y-123 and other Nb-doped samples. It was also found from Jc and Fp measurement, that the 0.01 wt.% Nb substation for the Y on YBCO superconductor improves the Jc and Fp.

Irreversibility Line and Enhancement of Magnetic Flux Pinning in Sm-Doped Y123 Superconductor with CuO Nanoparticles

Y1−xSmxBa2Cu3O7−∂ (x = 0.00, 0.01, 0.02 and 0.05 wt.%) samples with Nano-CuO have been prepared by the solid-state reaction method. The effects of Sm doped in the YBCO system with Nano-CuO (40 nm) on structural, critical temperature (Tc), irreversibility line (IL), critical current density, JC and flux line pinning force are investigated. We also measured magnetization as a function of temperature (M–T) and magnetic loops (M–H) at constant temperatures of 10, 20, 30, 40, 50 and 60 K up to 10 kG. XRD measurements show that all the sintered samples have orthorhombic structure. The sample with x = 0.01 wt.% Sm substituted for Y on YBCO superconductor improves the critical temperature more than that of the pure Y123 and the other samples. For this sample, the zero field-cooled and field-cooled magnetization as a function of temperature measurements reveals the shift of IL to higher temperatures and magnetic fields. The critical current density and flux pinning force calculated using the Bean’s critical state model indicate an enhancement of Jc and Fp for the Sm-doped x = 0.01 sample compared with the sample with x = 0.02 and even the pure Y123.

Conductivity Fluctuation and Some Parameters of High temperature Superconductor Polycrystalline Y1Ba2Cu3O7−δ doped with Silver Nanoparticles

In this study, we report the effect of Ag nanoparticles doping on the dimensional fluctuations of superconducting order parameters, crystal structure, and some parameters of Y1Ba2Cu3O7−δ + × Ag (x = 0.0, 0.06, 0.1, 0.3, and 0.6 wt%) polycrystalline ceramics. By increasing the content of Ag in YBCO matrix, X-ray diffraction (XRD) with the Rietveld refinement technique revealed that the crystal lattice parameters changed and the orthorhombicity decreased slightly. Also, the increase of Ag wt% caused a decrease of superconducting transition temperatures (Tc) which are determined from the standard four-probe method and dropped abruptly. Aslamazov–Larkin (AL) model was used to analyze excess conductivity fluctuation. Lawerence–Doniach (LD) temperature named TLD which is responsible for the dimensional nature of fluctuation inside the grains is influenced by nano-silver combination in the compound. Crossover temperature from 2D to 3D (TLD) decreased in the mean-field region as a resultant dominance of 3D region by increasing of Ag in YBCO matrix. The decrease in zero-resistance critical temperature (Tc zero), zero-temperature coherence length along the c-axis ξc(0), and super layer length d values implies the degradation of inter-grain weak links, more disorder state of samples and unsettling of the mean free path for the charge carriers respectively with addition of silver nanoparticles. The calculations based on AL and LD model showed the highest anisotropy (γ = 1.34681) for the x = 0.6 sample. The size of the Ag ions, being larger compared to Cu ions, and the number of substitution sites affects the coupling between the CuO2 planes and that results in higher anisotropy. Critical magnetic fields Bc1(0), Bc2(0), and critical current density Jc(0) were indirectly calculated from the Ginzburg–Landau (GL) number and GL equations. By increasing the doping level of silver nanoparticle, these parameters were found to be higher in Ag-added YBCO samples compared to the pure Y123, meaning better intrinsic flux pinning properties of doped Y123. The silver nanoparticle inclusion reduces the grain size and increases the strength and hardness of the parent compound.

Structural and superconducting properties of Y(Ba1-K )2Cu3O7-δ ceramics

Y(Ba1-xKx)2Cu3O7-δ ceramics (x = 0.00, 0.03, 0.05 and 0.08) were synthesized by thermal treatments of aqueous solution of metals nitrates and polyvinyl pyrrolidone (PVP) that acts as a capping agent. The effects of K-substitution on the crystal structure, microstructure and electrical resistance of samples were investigated. The X-ray diffractions results indicated an improvement of crystallinity and variation of lattice constant, a, b and c of YBa2Cu3O7-δ (Y123) phase with K-substitution. The K-substitution resulted in increasing of orthorhombicity factor compared to pure Y123. Microstructural observation using scanning electron microscopy showed that K-substitution promotes the grain growth of Y123. The superconducting transitions (Tc) of the substituted-samples were higher than that of the pure Y123. The Tc (onset) were 93, 97, 95, 95 K for the samples with x = 0.00, 0.03, 0.05 and 0.08, respectively. Comparing with pure sample, the substituted-samples showed sharper superconducting transition (ΔTc). The best superconducting properties was observed for sample with x = 0.03.

Influence of magnetic fields on the critical temperature of bulk YBCO superconductor with nanometer-sized Al<sub>2</sub>O<sub>3</sub> inclusions

YBCO specimens along with different amounts of nano-sized Al 2 O 3 were prepared using solid state reaction method. The structural characterization of all samples has been carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD patterns with Rietveld refinement procedure was used to characterize the samples crystal microstructure. SEM analysis revels the phases with distribution of Al 2 O 3 nanoparticles along the YBCO grain boundaries systematically. Superconducting parameters are affected by the nanoparticle addition, and results are discussed in bearing to the structural and microstructure differences between pure Y-123 and doped Y-123. The temperature dependence of electrical resistivity ρ (T) has been measured and the effect of addition of Al 2 O 3 nanoparticles with and without magnetic fields in the superconductivity and normal region has been reported. Keywords : YBa 2 Cu 3 O 7-δ ; Al 2 O 3 nanoparticles; critical temperature; magnetic fields.

Proximity effect induced by Kondo interaction in a network composed of YBCO and spin density wave

The possibility of the proximity effect mediated by Kondo interaction in YBCO embedded in system of diluted magnetic spin ordering has been studied. An YBCO sample is selected in which both metal to insulator transition and superconducting state exist in the different ranges of temperature. The intergranular network of the bulk Y-123 has been modified by the inclusion of YMnO3 which has a well defined magnetic structure depending on temperature. The current–voltage measurements have been carried out in pure Y-123 at several temperatures. At the same set of temperatures the current–voltage curves in presence of YMnO3 have been studied. The role of the diluted spin magnetic ordering in tuning proximity effect and conduction property in binary systems is associated with reduced coherence length in the normal region.

Superconducting Properties of Melt-Textured Growth YBa2Cu3O7−x Materials with Y211 Addition

Effects of Y211 phase addition into YBa2Cu3 O7−x bulk superconductors were investigated in order to provide high-quality grain structure for yttrium barium cop- per oxide (YBCO) bulk material. Various molar amounts of Y211 were added into Y123, and it was expected to affect the formation of the grains and to increase the crit- ical current density (Jc) and onset transition temperature (Tc) of YBCO. The samples were fabricated by using melt- textured growth (MTG) method and characterized in terms of ac magnetic susceptibility and superconducting quantum interference device (SQUID) magnetization measurements. A simple algorithm was used to calculate the critical cur- rent densities of the samples according to Bean's critical state model. According to addition of Y211 phases into pure Y123, bulk samples with different molar amounts showed that the highest critical temperature and critical current den- sity were obtained with a molar amount of n = 0.125 Y211-added sample as 94 K and 126.000 A/cm 2 , respec- tively, under the 1-T applied magnetic field at a temperature of 10 K.

Improvement on the melt-texturing performance of a (Y,Ta)0.5BaO3–YBa2Cu3Oy composite with superconductor applications

The aim of the article is to show the decrease in the peritectic temperature of a YBa2Cu3O7−d (Y123) superconductor phase with the Y0.5Ta0.5BaO3 (YTaBa) perovskite content. The decrease in the peritectic temperature is associated with the thermodynamic property between the Y123 and YBaTa perovskite phases (coligative property). Experimental results of the differential thermal analysis (DTA) and thermodynamic explanation are also provided. A slight displacement to a lower temperature range in the peritectic line suggests that the texturing of the Y123 material occurs under a lower temperature than the pure Y123. It seems that the required time for the melt-texturing is considerably decreased. This facilitates the performance in the texturing process. It is also found that the proposed Y123 superconductor is a potential top-seed in order to grow grains by the melt texture technique.

Effects of (La<sub>0.67</sub>Ca<sub>0.33</sub>MnO<sub>3</sub>)<i>x </i>(<i>x</i>= 0.0, 0.8, 1.0) Additions on the Structural and Superconducting Transition Temperature of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ </sub>System

The effect addition of manganites compound on the superconducting properties of YBCO was investigated through X-Ray diffraction (XRD), resistance-temperature (R-T) measurement, AC Susceptometer, and Scanning Electron Microscope (SEM). Samples with addition of (La0.67Ca0.33MnO3)x(LCMO) (x= 0.0, 0.8, 1.0) in YBa2Cu3O7-δ(YBCO) superconductor were prepared via solid state method. Addition of LCMO in YBCO superconductor changed the properties of samples. XRD analysis showed the addition of LCMO (0.8 wt% - 1.0 wt%) formed three new peaks of LCMO. The crystal structure is orthorhombic with space group Pmmm for pure Y123 but after addition 0.8 wt% and addition 1.0 wt% of LCMO the crystal structure was changed to tetragonal and space group P4/mmm. The temperature dependent of electrical resistance showed the samples were metallic above the transition temperature even though after addition. TheTc-onsuperconducting transition temperature decreased from 86 K to 84 K while theTc-offdecreased from 76 K to 70 K. Diamagnetic onset transition temperature,Tc-on(dia)decreased from 90.2 K to 89.8 K. This suppression was due to the magnetic behaviour of the LCMO addition. Morphology observation showed that the grain size and grains boundary are decreased while the porosity was increased as the addition of LCMOincreases.

Experimental and theoretical approaches on mechanical evaluation of Y123 system by Lu addition

This work is the continuation of a systematic study on the characterization of the Lu-added Y123 bulk superconducting materials prepared by the nitrate compounds and derivatives at 970 °C for 20 h. In this part, the effect of Lu inclusions on the physical and mechanical properties of the Y123 superconductors is examined with the aid of microhardness measurements performed at various applied loads in the range of 0.245–2.940 N. The microhardness measurement results allow us to determine the important mechanical characteristics such as Vickers microhardness, elastic (Young’s) modulus, yield strength and fracture toughness values being responsible for the potential industrial applications. It is found that all the properties given above are strongly dependent upon the Lu concentration in the Y123 matrix. Especially, Vickers microhardness (H v ) values of the samples studied in this work are found to suppressed considerably with the enhancement of the Lu addition in the system due to the degradation in the connectivity between superconducting grains. Moreover, the H v values of the pure Y123 sample are observed to increase with increasing the applied load whereas those of the Lu-doped superconducting materials are obtained to decrease with the load. In other words, the pure sample exhibits the reverse indentation size effect (RISE) behavior while the others obey the indentation size effect (ISE) feature, confirming the degradation in the mechanical properties with the Lu inclusions in the Y123 matrix. In addition, the microhardness measurement results are estimated using the 5 different models such as Meyer’s law, proportional sample resistance model, elastic/plastic deformation model, Hays–Kendall (HK) approach and indentation-induced cracking (IIC) model. According to the results obtained from the simulations, of the mechanical analysis models, the Hays–Kendall (HK) approach is determined as the most successful model for the description of the mechanical properties of the Lu-doped superconducting materials (exhibiting the ISE behavior) where both the both the reversible (elastic) and irreversible (plastic) deformations are produced. On the other hand, the IIC model is found to be superior to other approaches for the pure sample (presenting the RISE feature) where the irreversible deformation becomes more and more dominant compared to the reversible deformation.

The Effects of Sb Substitution on Structural Properties in YBa2Cu3O7 Superconductors

In this study, the effects of partial Sb3+ ion substitutions for the Y sites and the Cu sites on the superconducting properties of YBa2Cu3O y (Y123) ceramic superconductors were investigated. The samples were prepared by the conventional solid-state reaction method and the properties of the samples were investigated by means of X-ray diffraction, AC magnetic susceptibility measurements, scanning electron microscope, and energy dispersive X-ray analysis. The critical temperatures were determined to be in the range of 80–92 K for both Systems I and II. It was found that Sb-addition leads to the formation of the non-superconducting YBa2SbO6 phase, which has a negative effect on the critical temperature, since the highest critical temperature was measured for pure Y123. However, the increasing substitution level has a negligible effect on the X-ray diffraction analysis peak intensities of the superconducting phases. In addition, SEM images showed that Sb substitution decreases the grain size and modifies the microstructure development, which makes the samples denser.

Characterization of nano-composite M-2411/Y-123 thin films by electron backscatter diffraction and in-field critical current measurements

Thin films of nano-composite Y-Ba-Cu-O (YBCO) superconductors containing nano-sized, non-superconducting particles of Y2Ba4CuMOx (M-2411 with M = Ag and Nb) have been prepared by the PLD technique. Electron backscatter diffraction (EBSD) has been used to analyze the crystallographic orientation of nano-particles embedded in the film microstructure. The superconducting YBa2Cu3O7 (Y-123) phase matrix is textured with a dominant (001) orientation for all samples, whereas the M-2411 phase exhibits a random orientation. Angular critical current measurements at various temperature (T) and applied magnetic field (B) have been performed on thin films containing different concentration of the M-2411 second phase. An increase in critical current density Jc at T < 77 K and B < 6 T is observed for samples with low concentration of the second phase (2 mol % M-2411). Films containing 5 mol % Ag-2411 exhibit lower Jc than pure Y-123 thin films at all fields and temperatures. Samples with 5 mol % Nb-2411 show higher Jc(B) than phase pure Y-123 thin films for T < 77 K.

Enhancement of Critical Current Density in YBa2Cu3O7−y HTS Through Boron Addition

The effect of B2O3 addition on the superconducting transition and grain boundary critical current density of the boron free (control) and boron doped HTS ceramics with nominal composition YBa2Cu3BxO7−y (x=0, 0.025, 0.05, 0.075, 0.1 and 0.15) has been investigated. For the lowest-level boron doping (x=0.025) an increase by nearly 1.5 times was observed in the critical current density Jc compared to the control sample. The small additives of boron in YBa2Cu3BxO7−y (x=0.025 and 0.05) do not essentially affect the critical temperature Tc=92.5 K of nominally pure Y123. Higher-level boron added compounds revealed a decrease in both Tc and Jc values. The data obtained indicate the possibility of boron dopant being inserted either into interstitial or into substitutional sites of the lattice.

Hall anomaly in CNT-doped Y-123 high temperature superconductor

Abstract In order to study the Hall effect in pure and CNT-doped Y-123 polycrystalline samples, we have measured the longitudinal and transverse voltages at different magnetic field (0 − 9 T) in the normal and vortex states. In the normal state, the Hall coefficient is positive and decreases with increasing temperature, and can be approximately fitted to R H = a + bT −1 . We have found a sign reversal in the pure sample for the magnetic field of about 3 T, and double sign reversal of the Hall coefficient in the 0.7 wt% CNT-doped sample at about 3 and 5 T. The Hall resistivity in our samples depends on the pinning.

Structural and pinning properties ofY2Ba4CuMOy (M = Nb,Zr)/YBa2Cu3O7−δ quasi-multilayers fabricated by off-axis pulsed laser deposition

Power applications based on YBa2Cu3O7−δ coated conductors demand an enhancement of the critical current densityJc in magnetic fields to be achieved using artificial pinning centres. A well-known approach tostudying pinning by second phase nanoparticles is based on quasi-multilayer deposition ofYBa2Cu3O7−δ (Y123) and a dopant material. In this study we use theY2Ba4CuMOy (M = Nb, Zr; M2411) phase as a dopant material, which proved to be very successful in increasingJc for bulk samples. Although stability of the M2411 phase in bulk Y123 hasbeen reported, experimental evidence of its stability in thin films is stilllacking. We found that during the quasi-multilayer deposition, yttrium dopedBa(M1−xYx)O3 forms instead of the M2411 secondary phase, and this causes an increase ofJc at high magnetic fields as well as an increase in the irreversibility field below 80 K ascompared against pure Y123 thin films.

Increase of critical current density with doping carbon nano-tubes in YBa 2Cu 3O 7−δ

The effects of carbon nano-tubes (CNTs) on the crystal structure and superconducting properties of YBa 2Cu 3O 7− δ (Y-123) compound were studied. Samples were synthesized using standard solid-state reaction technique by adding CNT up to 1 wt% and X-ray diffraction data confirm the single phase orthorhombic structure for all the samples. Current–voltage measurements in magnetic fields up to 9 T were used to study the pinning energy U J and critical current density J c as a function of magnetic field at fixed temperature. We find that while T c does not change much with the CNT doping (91–92 K), both U J and J c increase systematically up to 0.7 wt% CNT doping in a broad magnetic field ranges between 0.1 and 9 T and J c in the 0.7 wt% CNT doped sample is at least 10 times larger than that of the pure Y-123. The scanning electron microscope image shows that CNTs are forming an electrical-network between grains. These observations suggest that the CNT addition to the Y-123-compounds improve the electrical connection between superconducting grains to result in the J c increase.

Phase separation, microstructure and superconductivity in theY1−xPrxBa2Cu3Oy compounds

High resolution synchrotron x-ray powder diffraction combined with micro-Raman spectroscopy areused to investigate the effect of Pr substitution for Y in optimally doped or overdoped polycrystallineYBa2Cu3Oy (Y123) compounds. The spectral analysis of the Raman-activeB1g-symmetry mode indicates a phase separation into coexisting nanoscopicenvironments consisting of pure Y123 and Pr123 and a mixed (Y–Pr)123phase of almost the nominal amount of Pr. The Y123 phase disappears atx≈0.6 where superconductivity is suppressed, while the formation of the pure Pr123phase is correlated with the increase of local lattice distortions at the Cu and Basites, the presence of crystal defects and the increase of microstrains, as obtainedby analyzing the anisotropic XRD peak broadening. The comparison of the BaAg-symmetry phononshift for the Y1−xPrxBa2Cu3Oy and YBa2−zPrzCu3Oy compounds as well as lattice dynamic calculations proves that, when Pr substitutes for Y,it also occupies an amount of Ba sites. The data from Pr, La or Ca substitution for Yindicate that loss of superconductivity is correlated with the substitution of Pr, La for Baand Ca for Y, though the underlying effects may not be the hole filling by theseoccupancies.

Magneto-transport characteristics of superconducting RBa2Cu3O7-delta multilayers and quasi-multilayers

To study flux pinning modulation due to intentional adjustments of rare earth cations, layer sequences and island-like secondary phases, we built up a series of artificial multilayers consisting of binary rare earth R123 as well as quasi-multilayers consisting of Y123/M (M = oxides such as Yttria Stabilized Zirconia) on single crystalline SrTiO3 by pulsed laser deposition. The field dependence of transport critical current density Jc was measured at various temperatures and directions of the applied magnetic field. Comparing with pure Y123 films, almost all present multilayers and quasi-multilayers showed a crossover behaviour of flux pinning, evidenced by an existing medium field (Hcro) below which Jc is lower than of pure Y123 films, whereas above Jc is higher. Furthermore, a strong temperature dependence of such a crossover field was observed. The higher the temperature, the higer Hcro, implying that an artificial tailoring of flux pinning may appear in a narrow range of fields as the mixed vortex state moves towards to the region of weak vortex glass and vortex liquid. However, the improvement of flux pinning is hardly observed in the state of strong vortex glass.

Flux line motion in superconducting(YBa2Cu3O7−d)1−x/(SiO2)x composite systems in high magnetic fields

Superconducting (YBa2Cu3O7−d)1−x/(SiO2)x (i.e.Y123/S) composites with x = 0, 0.05, 0.1, 0.15 and 0.2 were prepared by solid state synthesis. Detailed investigations ofstructural and electrical transport and magnetization in applied magnetic fields(B = 0–9 T) were carried out. The typical double-step superconducting transitions observed both resistively(B = 0) andmagnetically (B = 1 mT) reveal the granular nature of all the samples. The XRD,SEM and superconducting transitions show that addition ofSiO2 mainly influences the inter-grain regions of the samples, leaving the pure Y123 phase inintra-grain regions practically intact. This leads to an interesting behaviour ofM(T,B) andresistivity ρ(T,B) in the samples. The field-cooled (FC) magnetizationM(T) measuredat B = 1 mT shows a dip in the diamagnetic transition at a characteristic temperaturethat coincides with the onset of the second step in the zero-field-cooled (ZFC)M(T) measured in the same field. In the presence ofB≥1 T, the broadening of the superconducting transition revealed byρ(T) below the first step is found to be field-dependent, whereas below the secondstep at lower temperatures the broadening becomes field-independent. The width(ΔM) of the high fieldhysteresis loops (M–B) measured isothermally in the superconducting state initially varies as a power law ofB. Dependingon SiO2 content and temperature, the power law further deviates into either a shallow peak or amonotonically decreasing curve. We show that these results and a host of otherconsiderations point towards an interaction of vortices in inter- and intra-grain regions.