Zero-resistance Temperature Research Articles

Growth of (Cu,C)Ba2Ca2Cu3O9±δ thin films on flexible Hastelloy tapes

Abstract The applications of superconducting cable or magnet require that the superconductors are made into wires or tapes. For cuprate superconductors, this is a big challenge because of the friability and short coherence length of the materials; weak links are easy to be formed at the grain boundaries hindering the flowing of the supercurrent. One of the ways is to fabricate superconducting films on flexible metallic tapes with oxide buffer layers. The successful one so far is the REBa2Cu3O7 (RE=rare earth elements) films in tape form, as called the coated conductors. While the superconducting transition temperature of REBCO system is limited to around 90 K. Here we report the successful fabrication of another new non-toxic superconducting film, namely (Cu,C)Ba2Ca2Cu3O9±δ on these flexible metallic tapes with LaMnO3 and CeO2 as the top buffer layers. The onset superconducting transition occurs at 112 K and 110 K, and the zero-resistance transition temperatures are about 96 K and 98 K, respectively. The temperature dependent resistivity under magnetic fields in different directions reveals a relatively small anisotropy. Further optimization of the films will improve the zero resistance transition temperature, thus can also improve the characteristic properties for applications. Our results show that the (Cu,C)Ba2Ca2Cu3O9±δ is a promising candidate material for the high power applications in liquid nitrogen temperature region.

Synergistic Effects of BaTiO3 and MFe2O4 (M = Mn, Ni, Cu, Zn, and Co) Nanoparticles as Artificial Pinning Centers on the Performance of YBa2Cu3Oy Superconductor.

Large-scale superconductor applications necessitate a superconducting matrix with pinning sites (PSs) that immobilize vortices at elevated temperatures and magnetic fields. While previous works focused on the single addition of nanoparticles, the simultaneous inclusion of different nanoparticles into a superconducting matrix can be an effective way to achieve an improved flux pinning capacity. The purpose of this study is to explore the influence of mixed-nanoparticle pinning, with the co-addition of non-magnetic (BaTiO3; BT) and various types of magnetic spinel ferrite (MFe2O4, abbreviated as MFO, where M = Mn, Co, Cu, Zn, and Ni) nanoparticles, on the superconductivity and flux pinning performances of the high-temperature superconductor YBa2Cu3Oy (YBCO). An analysis of X-Ray diffraction (XRD) data of BT-MFe2O4-co-added YBCO samples showed the formation of an orthorhombic structure with Pmmm symmetry. According to electrical resistivity measurements, the emergence of the superconducting state below Tcoffset (zero-resistivity temperature) was proven for all samples. The highest Tcoffset value was recorded for the Y-BT-MnFO sample, while the minimum value was obtained for the Y-BT-ZnFO sample. Direct current (DC) magnetization results showed good magnetic flux pinning performance for all the co-added samples compared to the pristine sample but with some discrepancies. At 77 K, the values of the self-critical current density (self-Jcm) and maximum pinning force (Fpmax) for the Y-BT-MnFO sample were found to be eight times higher and seventeen times greater than those for the pristine sample, respectively. The results acquired suggested that mixing the BT phase with an appropriate type of spinel ferrite nanoparticles can be a practical solution to the problem of degradation of the critical current density of the YBCO material.

Superconducting thin films of [formula omitted][formula omitted][formula omitted][formula omitted] with zero-resistance transition temperature close to 100 K

High superconducting transition temperature is favorable for the applications of superconductors. Some cuprate superconductors have the transition temperatures above 100 K, such as the Hg- or Tl-based 1223 and 1234 phases, but many of them contain the toxic elements, like Hg and Tl. Meanwhile, the anisotropy of upper critical field or the effective mass of above mentioned Hg-, Tl-based systems, or the non-toxic Bi2Sr2Ca2Cu3O10 with Tc = 110 K is high, which makes the vortices easy to move and the irreversibility magnetic field is very low in the liquid nitrogen temperature region. Here we report the successful synthesis of the c-axis oriented (Cu,C)Ba2Ca2Cu3O9±δ superconducting thin film with the zero-resistance transition temperature reaching 99.7 K. The superconducting transitions are rather sharp as revealed by both resistivity and magnetization measurements. Temperature dependent resistivity has been measured under different magnetic fields, and the irreversibility lines have been achieved. The resistivity was also measured with the magnetic field rotated in the ac-plane, and the data can be nicely scaled by using the anisotropic Ginzburg-Landau model, yielding a temperature dependent anisotropy which varies from 17 at 110 K to 4 at 77 K. Additionally, the critical current density calculated from the magnetization-hysteresis-loops reaches about 6×105A/cm2 (zero field) at 77 K. Thus the film may be a good candidate for the applications of superconducting cables or high frequency superconducting filters in liquid nitrogen temperature region.

High-Temperature (Cu,C)Ba2Ca3Cu4Oy Superconducting Films with Large Irreversible Fields Grown on SrLaAlO4 Substrates by Pulsed Laser Deposition

(Cu,C)Ba2Ca3Cu4Oy is a nontoxic cuprate superconducting material with a superconducting transition temperature of about 116 K. Recently, it was found that bulk samples of this material synthesized under high pressure hold the highest irreversibility line among all the superconductors, which is very promising for its application in the liquid nitrogen temperature field. In this work, high-temperature (Cu,C)Ba2Ca3Cu4Oy superconducting films with large irreversible fields were prepared on SrLaAlO4(00l) substrates by pulsed laser deposition. The substrate temperature during deposition proved to be the most important parameter determining the morphology and critical temperature of the superconductors, with 680 °C considered to be the optimum temperature. X-ray diffraction (XRD) results showed that the (Cu,C)Ba2Ca3Cu4Oy films prepared under optimal conditions exhibited epitaxial growth with the a-axis perpendicular to the film surface and the b- and c-axes parallel to the substrate, with no evidence of any other orientation. In addition, resistivity measurements showed that the onset transition temperature (Tconset) was approximately 116 K, the zero-resistance critical temperature (Tc0) was around 53 K, and the irreversible field (Hirr) was about 9 T at 37 K for (Cu,C)Ba2Ca3Cu4Oy films under optimal temperature. This is the first example of the successful growth of superconducting (Cu,C)Ba2Ca3Cu4Oy films on SrLaAlO4(00l) substrates. This will facilitate high-performance applications of (Cu,C)Ba2Ca3Cu4Oy superconducting materials in the liquid nitrogen temperature field.

Effects of Mn and Ru substitutions on the electrical properties and AC susceptibility of Tl(BaSr)CaCu2O7 superconductor

In this paper, the effects of M = Mn and Ru substitutions at the Tl site of Tl[Formula: see text]Mx(BaSr)CaCu2O7 (Tl-1212) on the electrical properties and AC susceptibility were investigated. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) methods were used to examine the phase and microstructure, respectively. All samples showed diffraction patterns with Tl-1212 as the major phase and an increase in the Tl-1223 phase with increasing Mn and Ru substitutions. The microstructure showed partial melting and randomly oriented grains in all samples. The electrical resistance measurements showed metallic normal state behavior for all samples. The zero-resistance transition temperature [Formula: see text] was the highest for x = 0.4 where [Formula: see text] was 107[Formula: see text]K and 90[Formula: see text]K for Mn and Ru substitutions, respectively. The superconducting transition, [Formula: see text] obtained from AC susceptibility measurements increased with Mn and Ru substitutions up to x = 0.4. Using Bean’s model, the current density at the peak temperature of the imaginary part of the AC susceptibility, [Formula: see text]([Formula: see text] was determined to be between 16 and 22[Formula: see text]A[Formula: see text]⋅[Formula: see text]cm[Formula: see text] for Mn, and between 15 and 19[Formula: see text]A[Formula: see text]⋅[Formula: see text]cm[Formula: see text] for Ru-substituted samples. Mn substitution showed a higher transition temperature compared with Ru. This study showed that optimization of the average Cu valence was achieved with Mn and Ru substitutions for x = 0.4 at the Tl site. The ionic radii of the substituting and substituted elements are important factors in enhancing the transition temperature of Tl(BaSr)CaCu2O7 superconductor.

AC Susceptibility and Superconducting Properties of Te-Substituted TlSr<sub>2</sub>Ca(Cu<sub>2-x</sub>Te<sub>x</sub>)O<sub>7</sub>

The effect of Te substitution on TlSr2Ca(Cu2-xTex)O7 for x = 0.2, 0.3, 0.4, and 0.5 was investigated. The solid-state reaction approach was used to prepare the samples. All TlSr2Ca(Cu2-xTex)O7 samples exhibited the presence of major Tl-1212 and minor Tl-1201 phases. Further Te replacement promoted the formation of the Tl-1201 phase. All samples demonstrated metallic normal state characteristics before onset transition temperature, Tc-onset. The resistance versus temperature curve for all samples revealed that the Tc-onset was between 46 and 40 K and the zero-resistance temperature, Tc-zero was between 29 and 37 K. The measurement of AC susceptibility revealed a susceptibility superconducting transition Tc χ' ranging from 30 to 36 K. This study showed that Te substitution stabilized the Tl-1212 phase, enhanced Tc χ’ although the Tc-onset and Tc-zero were below the boiling point of liquid nitrogen.

A process for the preparation of high-quality and uniform large-scale Bi2212 superconducting films via the sol-gel method

Bi2212 high-temperature superconducting films (HTSFs) have garnered significant interest as a potential material for the development of high-Tc microwave and terahertz (THz) devices due to their intrinsic Josephson effect. This work presents the utilization of the polyvinyl pyrrolidone (PVP) -assisted sol-gel dip coating (PSGDC) method for the large-scale production of Bi2212 HTSFs. Initially, Bi2212 HTSFs were prepared on a small-scale single crystal (001)-oriented SrTiO3 substrates, and comprehensive characterization of their phase purity, crystal structure, surface morphology, microstructure, stress state, and transport properties was conducted as a foundation for further analysis. By optimizing the crystallization conditions and PVP content, the Bi2212 HTSF achieved improved performance, including a higher onset superconducting transition temperature (Tc, onset) of 94 K, zero-resistance temperature (Tc, zero) of 86 K, and a critical current density (Jc) of 6.8 × 104 A/cm2 under a zero magnetic field at 2 K. Subsequently, the optimized process was applied to successfully prepare a large-scale Bi2212 HTSF with a diameter of 50 mm, exhibiting uniform phase composition, surface morphology, and superconducting properties, expanding the potential applications of Bi2212 HTSFs.

Significantly enhanced superconductivity in monolayer FeSe films on SrTiO3(001) via metallic δ-doping.

Superconductivity transition temperature (Tc) marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For 2D superconductivity, the paired electrons condense into a coherent superfluid state at Tc, which is usually lower than the pairing temperature, between which intrinsic physics including Berezinskii-Kosterlitz-Thouless transition and pseudogap state are hotly debated. In the case of monolayer FeSe superconducting films on SrTiO3(001), although the pairing temperature (Tp) is revealed to be 65-83K by using spectroscopy characterization, the measured zero-resistance temperature ([Formula: see text]) is limited to 20K. Here, we report significantly enhanced superconductivity in monolayer FeSe films by δ-doping of Eu or Al on SrTiO3(001) surface, in which [Formula: see text] is enhanced by 12K with a narrowed transition width ΔTc ∼ 8K, compared with non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, we demonstrate lowered work function of the δ-doped SrTiO3(001) surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity. Our work provides a practical route to enhance 2D superconductivity by using interface engineering.

Direct evidence of high Tc superconductivity in glossy carbon films

Recent achievements and predictions in the field of intrinsic superconductivity in column IV-based covalent semiconductors and the nature of coupling, which determines the prospects for higher transition temperatures as well as the influence of disorder, are debated issues that can determine the future of the field. With this context, here we report the experimental findings of intrinsic superconductivity in glossy carbon (GC) films. These films are one of the forms of carbon materials obtained by pyrolysis of Pongamia glabra oil under high pressure and temperature. A zero-resistance state for films was observed at a critical Zero Resistance temperature of 134 K. Such relatively high superconducting critical temperature of films puts it among the superconductors with the strongest pairing strength between electrons and therefore an ideal material for investigations of high critical temperature superconductors.

Emergent superconducting fluctuations in compressed kagome superconductor CsV3Sb5

The recent discovery of superconductivity (SC) and charge density wave (CDW) in kagome metals AV3Sb5 (A = K, Rb, Cs) provides an ideal playground for the study of emergent electronic orders. Application of moderate pressure leads to a two-dome-shaped SC phase regime in CsV3Sb5 accompanied by the destabilizing of CDW phase. Nonetheless, the nature of this pressure-tuned SC state and its interplay with the CDW are yet to be explored. Here, we perform soft point-contact spectroscopy (SPCS) measurements in CsV3Sb5 to investigate the evolution of superconducting order parameter with pressure. Surprisingly, we find that the superconducting gap is significantly enhanced between the two SC domes, at which the zero-resistance temperature is suppressed and the transition is remarkably broadened. Moreover, the temperature-dependence of the SC gap in this pressure range severely deviates from the conventional Bardeen-Cooper-Schrieffer (BCS) behavior, evidencing for strong Cooper pair phase fluctuations. These findings reveal the complex intertwining of the CDW with SC in the compressed CsV3Sb5, suggesting striking parallel to the cuprate superconductor La2−xBaxCuO4. Our results point to the essential role of charge degree of freedom in the development of intertwining electronic orders, and thus provide new constraints for theories.

Enhanced superconducting transition temperature for Cr-substituted Tl2Ba2CaCu2O8-δ

Cr-substituted Tl2Ba2CaCu2O8-δ (Tl-2212) high temperature superconductor for x = 0–0.5 has been prepared using the standard solid-state reaction method. The precursor powders consisting of Ba2CaCu2Od were sintered at 900 °C for 24 h. The powders were then added with Tl and Cr, ground and pressed into pellets. The pellets were heated at 910 °C in oxygen flow for 4 min followed by furnace cooling. The d.c. electrical resistance (R) versus temperature (T) measurements were carried out using the four-point probe method with silver paste contacts. The transition temperature was determined from the slope of the resistance versus temperature graph. The superconducting critical region was divided into three: onset transition temperature (Tc-onset), middle transition temperature (Tc-mid) and zero-resistance temperature (Tc-zero). The non-substituted sample showed onset transition temperature, Tc-onset of 97 K. The x = 0.2 sample (Tl1.8Cr0.2Ba2CaCu2O8-δ) showed the highest Tc-onset (102 K). Further substitutions of Cr (x ≥ 0.3) decreased the transition temperature. All samples except the non-substituted samples showed at least two peaks in the dR/dT curves. This indicated that superconductivity within grains and intergrain occurred at different temperatures for all Cr-substituted samples. This work showed that Cr (x = 0.2) slightly enhanced the transition temperature of Tl-2212.

All-Chemical YBCO-Based Architecture Using a Simplified Multilayer Buffer Deposition

Chemical solution deposition (CSD) is a versatile and cheap technique widely used for both buffer layer and YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7−<i>δ</i></sub> (YBCO) epitaxial film growth. One of the main limits hindering the widespread use of the CSD technique in the field of coated conductors is the limited film thickness that can be reached without degradation. Among the different strategies adopted to obtain thicker film by CSD, increase of precursor solution concentration and viscosity can be mentioned. Another interesting approach is the use of multilayer deposition in order to overcome the limits of CSD technique. Multilayer deposition has been so far realized by performing a complete heat treatment - or at least a pyrolysis step - after each deposited layer, resulting in increased processing time and overall cost. In this contribution, we show that an epitaxial multilayer buffer can be easily obtained by means of multiple successive depositions, in which after each layer only a fast drying step of the precursor solution is carried out. In this way, only a single conversion heat treatment can be used. This approach not only allows a significant reduction on the processing time but also it is more suitable for the growth on metallic template. The viability of this approach is shown by using multilayer Zr-doped CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> buffer deposition on single crystalline YSZ substrate. It is shown that, up to 8 layers, no significant structural and morphological degradation of the buffer layer occurs. Further, YBCO film grown by CSD was used to test the suitability of multilayer buffer. YBCO film grown on multilayer buffer shows excellent superconducting properties, with zero-resistance critical temperature up to 92 K and a critical current density exceeding 1 MA/cm2 at 77 K in self field.

The Role of F-doping and the Sintering Temperature on the Superconductivity and Lattice Constants in LaOFeGe Compounds

The most prominent indicator of superconductivity is the superconducting transition temperature (Tc) that refers to three points. The onset transition temperature (Tonset) is defined as the deviation point away from the ρ(T) straight line (onset of the drop in resistivity). The midpoint transition temperature (Tmidpoint) is defined as the temperature, where resistivity becomes 50% of its value at Tonset. The zero-resistance transition temperature (Tρ≈0) is defined as the temperature, in which the resistance is identically zero or only immeasurably small. These indicators of temperatures associated with some factors. In this article, the X-ray diffraction and electrical resistivity measurements of LaO1-xFxFeGe samples are reported. This compound was successfully synthesized via a solid state reaction method with the presence of germanium Ge in the conduction layer. Furthermore, some factors affecting the superconducting transition temperature were studied, which are the F-doping dependence of Tonset, Tmidpoint, and lattice parameters, and sintering temperature dependence of Tonset.

Effect of buffer layer on thermal recovery of superconducting nanowire single-photon detector

Superconducting nanowire single-photon detectors (SNSPDs) wherein ultrathin films are fabricated on Si substrates are greatly affected by lattice mismatch between the thin film and the substrate. A buffer layer can be used to reduce such lattice mismatch or optimize the strain in the film, thereby improving device performance. We prepared and optimized Nb5N6 as a buffer layer and found that it considerably improved the properties of NbN films on Si substrates. The zero-resistance critical temperature (T C0) of a 3 nm thick NbN film with a 20 nm thick buffer layer was 10.3 K. SNSPDs with Nb5N6-buffered NbN films were fabricated and compared with normal devices; the fabricated devices had high hysteresis current and low timing jitter. Furthermore, we investigated the thermal diffusion process of the device based on the hysteresis current and hotspot relaxation time and found that Nb5N6 buffer layers enhance the thermal coupling between the superconducting film and substrates. The relaxation time of buffered SNSPD was 14.2 ps, which was shorter than that of nonbuffered SNSPD by 17.8 ps. These effects explain the performance improvement observed in the case of the buffered devices.

Enhanced Transport Critical Current Density of Tl-1212 Bulk Superconductor Added with Nickel-Zinc Ferrite Nanoparticles

High temperature superconductor Tl-1212 with nominal starting composition (Tl0.85Cr0.15)Sr2CaCu2O7-δ was prepared with high purity oxide powders using a solid state reaction method. Small amounts of nickel-zinc ferrite nanoparticles (Ni0.5Zn0.5Fe2O4) at compositions 0.01, 0.02, 0.05 and 0.10 wt. % were added into Tl-1212 superconductors. The effect of Ni0.5Zn0.5Fe2O4 nanoparticles’ addition on the critical temperature (Tc), transport critical current density (Jc), phase formation, and morphology was studied. The samples were characterized using electrical resistance measurement, transport critical current density measurement, powder X-ray diffraction method (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Zero-resistance critical temperature (Tc-zero) was found to rise from 97 K to 99 K with increasing Ni0.5Zn0.5Fe2O4 nanoparticles concentration. The highest value recorded for transport critical current density (Jc) was 3,120 mA/cm2 at 77 K, which exhibited by sample with 0.02 wt. % of Ni0.5Zn0.5Fe2O4 nanoparticles. All samples showed a dominant Tl-1212 phase and exhibited tetragonal lattice structure in the P4/mmm space group. SEM micrographs showed close-packed microstructure with low porosity. EDX mapping showed that Ni0.5Zn0.5Fe2O4 nanoparticles were well distributed in the Tl-1212 samples. This study demonstrated that Ni0.5Zn0.5Fe2O4 nanoparticles have functioned as effective flux pinning centers to Tl-1212 superconductors and thus significantly enhanced its Jc.

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content.

A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the critical transition temperature (TC) of B(P)SCCO by electroluminescence (EL) energy injection of inhomogeneous phases. However, the increase amplitude ΔTC () of TC is relatively small. In this study, a smart meta-superconductor B(P)SCCO with different matrix sizes was designed. Three kinds of raw materials with different particle sizes were used, and different series of Y2O3:Sm3+, Y2O3, Y2O3:Eu3+, and Y2O3:Eu3++Ag-doped samples and pure B(P)SCCO were prepared. Results indicated that the TC of the Y2O3 or Y2O3:Sm3+ non-luminescent dopant doping sample is lower than that of pure B(P)SCCO. However, the TC of the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminescent inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With the decrease of the raw material particle size from 30 to 5 μm, the particle size of the B(P)SCCO superconducting matrix in the prepared samples decreases, and the doping content of the Y2O3:Eu3++Ag or Y2O3:Eu3+ increases from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content enhances the ΔTC. When the particle size of raw material is 5 μm, the doping concentration of the luminescent inhomogeneous phase can be increased to 0.4%. At this time, the zero-resistance temperature and onset transition temperature of the Y2O3:Eu3++Ag doped sample are 4 and 6.3 K higher than those of pure B(P)SCCO, respectively.

Electrical properties and AC susceptibility of FeS added YBa2Cu3O7−δ superconductor

The opposing properties of superconductivity and magnetism are an interesting phenomenon. In this work, the effects of antiferromagnetic iron sulfide (FeS) addition on YBa2Cu3O7−δ superconductor were studied. Samples with nominal starting compositions YBa2Cu3O7−δ (FeS)x for x = 0–1.0 wt.% were prepared using the solid-state reaction method. X-ray diffraction patterns showed that the YBa2Cu3O7−δ phase and orthorhombicity were preserved with FeS addition. Scanning electron micrographs showed that addition of FeS decreased the average grain size while maintaining the grain morphology of granular structure. FeS does not suppress the onset transition temperature, Tc onset and AC susceptibility transition temperature, Tcχ, which were found to be in the range of 89–92 K and 92–93 K for all samples, respectively. However, the peak temperature, Tp of the imaginary part of the susceptibility and zero-resistance temperature, Tc zero were severely suppressed with FeS addition. The critical current density at the peak temperature of the imaginary part of the susceptibility, Jc(Tp) for all samples were calculated to be in the range of 16–19 A/cm2. This work showed that FeS affected the connectivity between the grains which weakened the intergranular coupling and decreased the flux pinning energy.

Significance of Cobalt Ferrite Nanoparticles on Superconducting Properties of Tl-1212 High Temperature Superconductor

Thallium-based high temperature superconductor (HTS) with nominal starting composition (Tl0.85Cr0.15)Sr2CaCu2O7-δ (Tl-1212) was prepared using high purity oxide powders via solid state reaction method. Small amounts (0.0 – 0.15 wt. %) of cobalt ferrite nanoparticles (CoFe2O4) were added into Tl-1212 superconductors. The effect of CoFe2O4 nanoparticles addition on the critical temperature (Tc), phase formation and microstructure properties including elemental compositional analysis were studied. The samples were investigated by the characterization of electrical resistance measurement, powder X-ray diffraction method (XRD), scanning electron microscopy and energy dispersive X-ray analysis (EDX). Zero-resistance temperature (Tc-zero) was found to reduce from 97 K to 89 K with increasing of CoFe2O4 nanoparticles concentration. Most of the samples indicated a dominant Tl-1212 phase of a tetragonal structure with a minor phase of Tl-1201. SEM micrographs with EDX mapping showed that CoFe2O4 nanoparticles were well distributed in all the samples.

Synthesis and characterization of Eu- and La-doped CuS nanoparticles and their effects on the electrical properties of (Bi,Pb)2Sr2Ca2Cu3Oδ superconductor

Undoped, Eu- and La-doped CuS nanoparticles stabilized by l-cysteine were synthesized by a low-temperature soft aqueous route. Their structural properties were investigated by X-ray powder diffraction, their morphological properties were scrutinized using scanning electron microscopy, their microstructural properties were carried out using transmission electron microscopy, their optical properties were examined using ultraviolet–visible spectroscopy, and their electrical properties were studied using complex impedance spectroscopy. It was found that Cu0.99La0.01S nanoparticles exhibit the smallest particle size, the highest optical bandgap, the highest values of electrical conductivity and dielectric constant, and the lowest values of dielectric loss tangent when compared with CuS and Cu0.99Eu0.01S nanoparticles. To investigate the effect of the as-synthesized nanoparticles on the superconducting properties of bismuth-based compound ((Bi,Pb)2Sr2Ca2Cu3Oδ), its structural properties were examined by X-ray powder diffraction, its transport properties were analyzed by the standard four-probe technique, its intrinsic properties were investigated using the Aslamazov–Larkin approach and its pinning properties were studied using the thermally activated flux flow model. It was found that Cu0.99La0.01S added sample exhibits the highest Bi-2223 phase concentration, the lowest residual resistivity, the highest critical transition temperature, the lowest value of coherence length, the highest values of penetration depth, upper critical magnetic field and critical current density, the narrowest shift of the zero-resistivity temperature, the highest effective pinning energies and the highest global critical current densities, when compared with pure, CuS and Cu0.99Eu0.01S added samples.

Phase Formation and Conductivity Fluctuation Investigation in Nanoparticle SnO2-Added Y3Ba5Cu8O18 ± δ Polycrystalline Superconductor

The influence of 0, 0.20, 0.40, 0.50, and 0.60 wt % nano-sized tin oxide (SnO2) particles on electrical conductivity fluctuation in normal and superconducting state of the Y3Ba5Cu8O18 ± δ (denoted as Y‑358) polycrystalline samples is studied. Phase formation and microstructures have been systematically examined. By increasing the content of SnO2 in YBCO matrix, X-ray diffraction technique showed slight variation in lattice parameters and overall reduction in the orthorhombicity. Scanning electron microscopy observations and the crystallite size calculation also revealed that the grain size and the average crystallite size decreased compared to the SnO2-free sample. Aslamazov–Larkin and Lawrence–Doniach prototypes were used to analyze conductivity fluctuations based on the electrical resistivity ρ(T) measurements. Superconducting transition temperatures TC and TLD have been reported. The influence of SnO2 addition on the superconducting properties indicates that with the addition of SnO2 nanoparticles into Y-358 compound, some parameters values such as zero-resistance critical temperature TC zero, coherence distance alongside the c axis at 0 K ξc(0), and super-layer length d decrease in total, while anisotropy γ, critical magnetic fields Bc1(0), Bc2(0), and critical current density Jc(0) increase in SnO2-added Y-358 specimens compared to the pure one. The reasons corresponding to these scenarios are discussed in details.