Pure YBCO Sample Research Articles

Enhanced superconducting properties of multi-wall carbon nanotubes added YBCO-123 Superconducting System

We investigated multi-wall carbon nanotubes (MWCNT’s) adding in Y1Ba2Cu3Ox high temperature superconductor system. We used solid-state method for sample preparation and 0.0 < x < 5.0 wt% MWCNT’s were added to the main matrix. Structural evolution, electrical transport and magnetic properties of material produced was investigated. According to the results obtained the superconducting onset temperature, Tconset, was not changed excessively, however, it was observed that the transport critical current density, Jctran, increased by at least 6-fold compared with the pure YBCO samples. Magnetic properties of material were also investigated by means of magnetization measurements up to 9 T together with the I–V measurements and pinning force, Fp, calculations.

Effect of Au nano-particles doping on polycrystalline YBCO high temperature superconductor

In this research, we prepared different Au nanoparticles (0.1–2wt%) doped YBCO high temperature superconductor samples by sol-gel method. To characterize the samples, we used X-Ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Results show the formation of orthorhombic phase of superconductivity for all prepared samples. We observed that by adding Au nanoparticles, the grains' size of the samples reduces from 76nm to 47nm as well. The critical current density (Jc) and transition temperature (Tc) were determined using current versus voltage (I–V) and resistivity versus temperature (ρ-T) measurements, respectively. We found that by increasing Au nanoparticles in the compound, in comparison to the pure YBCO sample, the transition temperature, pinning energy and critical current density will increase. Also, the highest Jc is for 1wt% Au doped YBCO compound that its critical current density is about 8 times more than the Jc of pure one in 0.7T magnetic field.

Measurement of Vortex Pinning in YBCO and YBCO/BZO Coated Conductors Using a Microwave Technique

In order to study the effect of pinning in coated conductors, we have used pulsed laser ablation to grow $\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-x}$ (YBCO) and $\text{YBa}_{2}\text{Cu}_{3}\text{O}_{7-x}/\text{BaZrO}_{3}$ (YBCO/BZO) films on metallic templates. Despite the complexity of the structure, after the optimization of the deposition procedure, the YBCO/BZO showed only a moderate reduction of $T_{c}$ with respect to the pure YBCO sample. We use a very high frequency (∼47.7 GHz) dielectric resonator technique in order to induce very short distance vortex shaking, thus probing the steepness of the potential well. We report on measurements of the microwave response of the superconducting structures in terms of the quality factor $Q$ and the frequency resonance $\nu_{0}$ as a function of a moderate dc magnetic field $H$ , at different temperatures $T$ . To keep as much contact as possible to the raw data ( $Q$ and $\nu_{0}$ ), in agreement with a generalized model for vortex dynamics, we determine the pinning parameter $r$ and the upper limit for the creep factor $\chi_{M}$ . Based on the field dependence of the pinning parameters, the vortex pinning regimes were discussed. We find that the improvement of pinning by BZO is much reduced with respect to the effect observed in films grown on single crystals. In particular, the reduction of the critical temperature must be taken into account in order to appreciate the results.

Investigation of the properties of carbon-base nanostructures doped YBa2Cu3O7−δ high temperature superconductor

In this research, we have investigated the effects of three samples of carbon-base nanostructures (carbon nanoparticles, carbon nanotubes and silicon carbide nanoparticles) doping on the properties of Y1Ba2Cu3O7−δ (YBCO) high temperature superconductor. The pure and doped YBCO samples were synthesized by sol–gel method and characterized by resistivity versus temperature (ρ–T), current versus voltage (I–V), through X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The results confirmed that for all the samples, the orthorhombic phase of YBCO compound is formed. We found that the pinning energy and critical current density of samples increase by adding carbon nanostructures to YBCO compound. Also critical temperature is improved by adding carbon nanotubes to YBCO compound, while it does not change much for carbon and silicon carbide nanoparticles doped compounds. Furthermore, the samples were characterized by UV–vis spectroscopy in 300K and the band gap of the samples was determined. We found that the carbon nanotubes doping decreases YBCO band gap in normal state from 1.90eV to 1.68eV, while carbon and SiC nanoparticles doping increases it to 2.20 and 3.37eV respectively.

Improvement of Critical Current Density in YBa2Cu3O7-δ Superconductor with Nano TiO2 Addition

The optimization of flux line pinning in superconductors is one of the most efficient ways to improve the transport properties of these materials. In this work, we have examined the effectiveness of an insulating nano particle inclusion in a type II superconductor as a pinning center with a size close to the coherence length, ξ. We report on measurements of the superconducting properties of YBa2Cu3O7-δ bulk superconductors with different weight % of nano particles of TiO2 contents (x = 0–3wt %) prepared by the modified combustion route. The microstructure of bulk YBCO added with nano particles was characterized by scanning electron microscopy. Sub-micron, randomly oriented particles of this phase were found to form around grain boundaries and within YBCO grains in bulk sintered pellets. It is observed that the critical current density is higher by a factor of 3 and the Jc–B behavior is remarkably improved in samples with nano additions. However, the superconductor transition temperature (Tc) slightly decreases from 92K to 90.5K. The flux pinning force is enhanced by 8 times that of pure YBCO sample. Thus these nano particles are effective flux pinning centers and enhance the transport critical current density at liquid nitrogen temperature for an applied magnetic field. The experimental results suggest that the added nano-sized TiO2 particle may have high pinning efficiency at a temperature around 77K.

Enhancement of Vortex Pinning in YBa2Cu3O7−δ -BaHfO3 Superconductor-Insulator System

A systematic study on phase evolution, bulk density, resistivity, critical transition temperature (T C), critical current density (J C) and in-field transport critical current density (J C–B) of pure and nano particles of BaHfO3 added YBa2Cu3O7−δ (YBCO) samples of different weight percentages has been carried out. The result shows a significant improvement in the electrical transport properties of the superconductor, namely the J C, J C–B characteristics and flux pinning force (F p) of the BaHfO3 added samples. The transition temperature also was found to increase marginally. A maximum transport J C of 742 A/cm2 at 77 K (for x=2 wt%) was observed for BaHfO3 added samples against 147 A/cm2 for pure YBCO sample. The enhancement of the critical current density in the YBCO–BaHfO3 sample is attributed to the formation of an insulating and non-reacting YBa2HfO5.5 phase, acting as artificial pinning centers in the matrix. The introduction of nano particles of BaHfO3 in bulk YBCO increases the pinning force density from 30×103 N/m3 to 424×103 N/m3 at 77 K. The improvement in sintering density due to an optimum value 2 wt% BaHfO3 addition in bulk YBCO indicates its potential use in electrical devices and technology. The enhancement in the superconducting properties, particularly in the J C–B characteristics due to BaHfO3 addition, seems to have great technological significance.

Effects of TFA addition on the growth of sintered YBa2Cu3Oy superconductors

Abstract The effects of trifluoroacetic acid (TFA) addition on the growth of a superconducting phase in sintered YBCO samples were investigated. YBCO samples with TFA addition were prepared by adding TFA (99.0%) to YBCO powder and then pressed into pellets and heated 1173 K – 1213 K for 12 - 20 hr in air. After the heat treatment, the TFA-added sample showed large grain sizes and highly c -axis oriented structures compared to pure YBCO samples, which indicates the enhancement of the grain growth of YBCO sintered samples by the TFA addition. The J c (0) value and J c/ J c (0T) properties of the sintered samples was improved by the TFA addition.

Performance of high temperature superconducting ceramic/thermoplastic polymer composites

Abstract A technique for preparing flexible composites by dispersing high Tc yttrium based superconductor filler in a polyethylene matrix with transition temperature of about 90 K has been developed. Susceptibility measurements demonstrated a high degree of field exclusion, indicating that the superconducting behavior is preserved in the yttrium barium copper oxide (YBa2Cu3O7-×) filler material. It is found that all the composites showed the diamagnetic transition at around 90 K, which is the same as that of the pure YBCO sample. The single transition for both the parent YBCO material and the composite samples indicates the dominant presence of isolated superconducting grains within such samples. A large drop in resistivity with increasing filler content is observed for all the ceramic-polymer systems investigated in this study. At low percentages of the filler, the composite behaves as an insulator with very low conductivity. No dc zero resistance transition is observed. The absence of zero resistance in these composites was presumably due to the absence of appropriate contacts between the superconducting grains and the lack of a conductive path necessary for a zero resistance transition to occur.

Investigation of flux pinning properties of YBCO:BaZrO 3 composite superconductor from temperature dependent magnetization studies

Magnetization studies of YBCO:BaZrO 3 composite superconductor have been done over a wide range of temperature and applied magnetic field using MPMS SQUID VSM and the results are compared with that of pure YBCO. The analysis of the observed results indicate that there is considerable improvement in the values of critical current density ( J C ) and pinning force density ( F p ) of YBCO:BaZrO 3 composite samples as compared to pure YBCO sample in the entire investigated range of applied magnetic field and temperatures ranging from 4 to 77 K. The variation of J C with reduced temperature t (= T/ T C ) for the composite samples has been found to be similar to that of pure YBCO sample indicating similar nature of the vortex interaction with pinning centres in both pure and composite samples. The enhancement in the value of J C and F p in the composite samples as compared to pure YBCO sample has been attributed to the increased defect density in the composite samples due to the presence of BZO particles in YBCO matrix.

Improved critical current density in Zn doped YBCO single crystals

Magnetic measurements were made using pure YBCO and Zn doped YBa 2(Cu 1− x Zn x ) 3O 7− σ . Single crystals with Zn concentration of 0.5%, 1.5%, 3.0% and 4.3%. The magnetic hysteresis loops for these samples were measured in the temperature range 0.1 ⩽ T/ T c ⩽ 0.96 under magnetic fields of 5 T using SQUID. It was found that the critical current density J c increased for low Zn content samples up to 3% Zn concentration compared to pure YBCO sample and decreased for the higher Zn content samples. These values varied consistently when compared at magnetic fields of 1 T and 3 T. Moreover Zn doped samples showed significant values of J c in the temperature range of 0.7–0.9 T c , close to critical temperature compared to pure YBCO sample. The irreversibility field H irr was also enhanced in this temperature range showing consistent decrease with increase of Zn concentration. The peak field H p above H c 1 and irreversibility field H irr , both show power law dependence of the form H = m 1(1 − T/ T c ) m 2 in the temperature range of 0.75–0.96 T c . The values of parameter m 2 increased from 1.44 to 1.95 for the samples up to 3% Zn content and decreased to 1.37 for higher Zn contents. The ratio H irr / H p was found to be 3–4 for the lower Zn content samples and was 7–8 for the sample with high Zn content indicating more disorder for higher Zn content samples. The region between peak field H p and irreversibility field H irr was broadened with the increase of Zn concentration. The strong effect of Zn substitution in modifying behavior of these samples even at elevated temperatures is possibly due to the changes in the anisotropy of our samples with the increase of Zn concentration and also due to the locally induced changes in magnetic moments by Zn substitution.

Strongly enhanced pinning force density in YBCO–BaTiO 3 nanocomposite superconductor

YBa 2Cu 3O 7−δ–BaTiO 3 (4 wt.%) (YBCO–BTO (4%)) composite bulk polycrystalline sample has been synthesized by solid state reaction method. The structure of composite sample has been investigated by X-ray diffraction and magnetization measurements were carried out using MPMS SQUID VSM. The superconducting transition temperature of the YBCO–BTO (4%) sample was similar to that of pure YBCO. The critical current density ( J c ) for YBCO–BTO (4%) sample increases significantly as compared to pure YBCO sample. The enhancement of the critical current density in the YBCO–BTO (4%) sample has been attributed to the presence of BaTiO 3 nanoparticles acting as artificial pinning centres. The introduction of BaTiO 3 particles in YBCO increases pinning force density from 0.71 GN/m 2 to 1.41 GN/m 2 at 4 K and 0.33 MN/m 2 to 0.97 MN/m 2 at 77 K.

Incorporation of double artificial pinning centers in YBa 2Cu 3O 7−δ films

YBa 2Cu 3O 7−x + BaZrO 3 + Y 2O 3 (YBCO + BaZrO 3 + Y 2O 3) mixed films were prepared on SrTiO 3/MgO substrates by pulsed-laser deposition from an YBCO + BaZrO 3 target with a thin Y 2O 3 sector stuck on the top. The pinning properties for the double-doped YBCO + BaZrO 3 + Y 2O 3 thin film were enhanced in comparison with a pure YBCO sample prepared in the same experimental conditions. The maximum global pinning forces F P for the double-doped sample are 12.8 GN/m 3 at 77K, 46.3 GN/m 3 at 65K, and 122 GN/m 3 at 40K. In the double-doped sample, the angular dependence of J c showed a broad peak at B//c due to the flux pinning by c-axis correlated defects, combined with a plateau, due to the flux pinning by isotropic pinning centres. Consistently, both BaZrO 3 nanorods parallel to the c-axis and Y 2O 3 nanoparticles randomly dispersed inside the YBCO matrix were observed in TEM images.

Incorporation of double artificial pinning centers inYBa2Cu3O7−d films

YBa2Cu3O7−x+BaZrO3+Y2O3 (YBCO+BaZrO3+Y2O3) mixed filmswere prepared on SrTiO3/MgO substrates by pulsed-laser deposition, with anYBCO+BaZrO3 targetwith a thin Y2O3 sector stuck on the top. The pinning properties for the double-dopedYBCO+BaZrO3+Y2O3 thin film were enhanced in comparison with those of a pure YBCO sample preparedin the same experimental conditions. The maximum global pinning forcesFp for the double-dopedsample are 12.8 GN m−3 near3 T at 77 K, 46.3 GN m−3 near4 T at 65 K, and 122 GN m−3 near 9 T at 40 K. In the double-doped sample the angular dependence ofJc showed a broad peak at , due to the flux pinning by c-axis correlated defects, combined with a plateau, due to the flux pinning by isotropic pinning centers. BothBaZrO3 nanorodsparallel to the c-axis and Y2O3 nanoparticles randomly dispersed inside the YBCO matrix were consistently observed inthe cross sectional transmission electron microscopy images.

A study of grain orientation of Alkali doped polycrystalline YBCO ceramics using an EBSD technique

Polycrystalline KClO 3-, K 2CO 3-, Rb 2CO 3-doped and undoped YBa 2Cu 3O 7− x (YBCO) ceramic high- T c superconductors were examined using electron backscatter diffraction (EBSD) technique. We present orientation maps and pole figures of the samples. It is shown that the pure YBCO samples and the ones with Rb 2CO 3 and K 2CO 3 additives do not exhibit a very pronounced texture (i.e. preferred orientation). On the polycrystalline KClO 3-doped YBCO samples we find two major grain orientations (0 0 1) and (1 0 0) normal to the sample surface while the pure YBCO sample does not exhibit any orientation maxima. This observation is ascribed to the effect of a liquid phase due to the KClO 3-additive during the preparation process.

63,65Cu nuclear quadrupole resonance study of Ni-doped YBa 2Cu 3O 7

We have prepared pure YBCO (YBa 2Cu 3O 7− δ ) and Ni-doped YBCO (YBa 2− x La x Cu 3− x Ni x O 7− δ , x=0.1) samples and performed 63,65Cu nuclear quadrupole resonance (NQR) measurements. La substitution introduced for charge compensation, as well as Ni doping, severely distorts the electric field gradient at the copper sites inducing extra 63,65Cu NQR peaks other than the main peaks, for both the plane and the chain sites. 63,65Cu NQR linewidths for the plane site increased significantly whereas those for the chain site remained similar. Furthermore, both the spin–lattice and the spin–spin relaxation times for the plane copper decreased whereas those for the chain copper increased. The Ni substitutional effects on linewidths and relaxation times confirm that Ni carrying a local moment substitutes for the plane copper.

Flux Pinning in PMP Y－Gd－Ba－Cu－O Superconductors

利用X射线衍射、扫描电镜和SQUID磁强计研究了粉末熔化(PMP)YBa\-2Cu\-3O\-y和掺Gd 的YBCO超导体的微结构，超导性能、磁通钉扎特性及鱼尾效应等，发现在掺杂Gd的样品中当 温度低于70?K时出现鱼尾现象(H⊥c)，而在纯YBCO中无鱼尾出现.添加Gd有助于提高 J\-c，增强钉扎，并认为由掺Gd所引起的Y\-2BaCuO\-5粒子尺寸的减小，应力场钉扎和 磁性钉扎是J\-c增加的原因.

Thermal conductivity of Pr doped YBa2Cu3Oy and a quasiparticle contribution

The thermal conductivity κ of Pr doped YBa2Cu3Oy (Y1−xPrxBa2Cu3Oy) polycrystals has been studied as a function of temperature from 10 K up to 150 K. A pure YBCO crystal exhibits a clear enhancement in κ belowT c but for highly Pr doped samples (x>0.2) the temperature dependence of κ monotonically decreases with reducing temperature. Furthermore, the value of κ of insulating PBCO (x=1.0) is strongly suppressed compared with that of superconducting YBCO. Such behaviour is not explained by the electron-phonon interaction model proposed by Bardeen, Rickayzen and Tewordt but suggests a picture in which an observed peak belowT c in κ of the pure YBCO sample is ascribed to a quasiparticle contribution.

Phonon Raman scattering and structure of Co substituted YBa2Cu3O6+δ

Raman and x-ray diffraction measurements have been performed on Co substituted YBa2Cu3−xCoxO6+δ. The x-ray diffraction data show that the structure transforms from orthorhombic to tetragonal at x∼0.13. The features in the Raman spectra change smoothly throughout the investigated concentration range without any observable abrupt changes at the phase transition. The observed changes in the Raman spectra for increasing Co concentration are reminiscent of those observed for pure YBCO samples of increasing oxygen deficiency. In particular, the frequency of the O(4) stretching vibration is observed to be similarly correlated to Tc for both Co substituted and oxygen deficient YBCO. It is suggested that the O(4) stretching vibration is sensitive to small changes of the charge balance between the CuO chains and the CuO2 planes.

ON THE SPECIFIC HEAT ANOMALIES IN THE TEMPERATURE RANGE 200 K TO 240 K IN CuO AND YBa2Cu3O7−δ(YBCO)

Specific heat anomalies in YBa 2 Cu 3 O 7−δ (YBCO) and CuO were investigated in the temperature range 200 K to 240 K. It was found that small amounts of CuO contained as a separate phase in YBCO produce easily observable anomalies caused by two consecutive antiferromagnetic (AF) transitions at 211.6 K and 228.3 K in CuO. The anomalies hence were observed in both pure CuO and YBCO samples containing some free CuO. The anomalies found here are of a different character than the broad peak we observed earlier around 220 K in pure ceramic YBCO. This lends support to the earlier interpretation of the 220 K anomaly as a structurally related one.