Ceramic High-temperature Superconductors Research Articles

Analysis of technology methods and study of properties of high-temperature superconducting ceramics based on YTTIRIUM

Based on the analysis of the studied properties, the paper presents the developed technology for the manufacture of high-temperature superconducting (HTSC) ceramics based on ultrafine powders; in this case, the method of dry pressing under the influence of an ultrasonic signal is considered. Based on the analysis, the optimal technology variants for synthesizing HTSC ceramics were selected. Data are presented on the performance properties of HTSC ceramics, samples of electromagnetic field screens, volumetric microwave resonators, and ceramic squids. Also, a method of positron annihilation is described, measuring the lifetime of positrons and measuring the curves of the angular distribution of annihilation photons (ADRP), which makes it possible to identify defects of the vacancy type (vacancies, clusters of vacancies, loops, dislocations).

Thermally activated flux flow and inter-granular coupling properties in superconducting (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1−x (ZnO NPs)x composites

In high-temperature ceramic superconductors, vortices motion is induced by the strong thermal fluctuations because of the thermally activated flux flow (TAFF). The TAFF impedes the transport properties and critical current density of superconductors. It has been reported that adding nano-scale impurities can induce artificial pining centers that may improve inter-granular connections and flux pinning strength in ceramic superconductors. Here, the effects of different amounts (0.0–1.0 wt%) of ZnO nanoparticles on the TAFF behavior and zero temperature activation energy of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconducting phase have been studied using the modified TAFF model. Moreover, the impacts of the additive on the inter-granular traits and the Josephson coupling energy of the superconducting phase have been investigated using AC susceptibility measurements. Vortex phases analysis indicates that all composites show a vortex glass to vortex liquid phase transition at Tg. The vortex liquid phase is divided into the critical region existing in a finite temperature region just above Tg and the TAFF region present in the finite temperature region above it. It was found that the TAFF region is shifted to the higher temperatures and gets narrower, as the ZnO nanoparticles concentration enhances from 0.0 to 0.2 wt%. The vortex glass to vortex liquid transition temperature, Tg, increases from 93.8 K for the sample without additive to 101.0 K for the composite with 0.2 wt% ZnO nanoparticles. In addition, the zero-temperature activation energy (U0/KB) increases from ~0.4 × 105 K for the sample without additive to ~1.4 × 105 K for the composite with 0.2 wt% ZnO nanoparticles and then decreases for more ZnO concentrations. Moreover, it was found that the Josephson coupling energy Ej increases from ~0.039 eV for the sample without additive to ~0.136 eV for the composite with 0.2 wt% ZnO nanoparticles. These results point out a significant enhancement of the activation energy, flux pinning capability, and inter-granular coupling of the Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconducting phase with the addition of the 0.2 wt% ZnO nanoparticles.

Plasmon resonance at the interface dielectric - nanocomposite material with superconducting inclusions

This article theoretically considers surface plasmon resonance in composite structures. The features of the surface plasmon resonance arising at the interface with media containing nanoparticles from a high-temperature superconductor are investigated. The dielectric constant of spherical superconducting inclusions is considered taking into account Gorter-Casimir two-fluid model. The temperature dependence of the electrodynamic parameters of the superconductor is taken into account. The two-fluid model, the dependence of the concentration of non-superconducting electrons in a superconductor is often used as the fourth power of temperature nn~T4. In this work, a phenomenological model is used, according to which the electron concentration of non-superconducting electrons in a superconductor is determined by the formula nn~Tγ with γ=1.3÷2. This model is in good agreement with experimental data for high-temperature ceramic superconductors. The dispersion characteristics of surface plasmons arising in a planar structure with a thin nanocomposite superconductor layer are investigated. It is shown that the dispersion characteristics depend significantly on temperature.

Resistance of High-Tc Superconductors: Review Article

"The origin of resistance and its relation to the superconducting mechanism remain a profound, unsolved mystery. Currently, model parameters used to fit normal state properties are specific and vary arbitrarily from one doping. This short review illustrates the electrical resistivity of ceramic high temperature superconductors copper oxides. The article gives a summary of the prevailing arguments of researchers to relate the material to ceramic HTS compounds. Keywords: superconductivity, HTC ceramic compounds, resistivity. "

Shear Elastic Properties of HTSC Ceramics in the Region of Superconducting Transition

The shear elastic properties of YBa2Cu3O7 –x high-temperature superconducting (HTSC) ceramics are studied near the superconducting transition at a temperature of 91.3 K and room temperature of 293 K. For the first time, a local increase in shear nonlinear acoustic parameter N in the region of the phase transition temperature was detected. Experimental studies of the linear and nonlinear elastic properties of YBa2Cu3O7 –x HTSC ceramics in the region of the superconducting transition showed that the electronic phase transition has a significant effect on its elastic properties. Based on experimental measurements, linear and nonlinear elastic parameters are determined both at room temperature and in the region of the phase transition.

Device for Increasing the Magnetic Flux Pinning in Granular Nanocomposites Based on the High-Temperature Superconducting Ceramic

A device for modifying the granular high-temperature superconducting ceramics in the plasma of a low-pressure arc discharge has been considered. The particular features of the design and operational principle of this device have been described. The device made it possible to combine the synthesis of that play a role of additional pinning centers and simultaneous deposition of these nanoparticles on microgranules in a single processing cycle. The experimental results on the effect of additional pinning centers on an increase in the critical current thanks to the formation of self-assembled structures in the form of whiskers have been considered.

HTS Multimaterial Gradiometer Modules for YBa2Cu3O7 SQUID Systems

For the measurement of very small magnetic fields, systems based on superconducting quantum-interference devices (SQUIDs) have been manufactured and employed for many years. In liquid helium operated systems with niobium SQUIDs, wire wound gradiometers can be coupled to a shielded SQUID, but in ceramic high-temperature superconductors (HTS) this is not a common setup, since appropriate thin HTS wires with a bending radius of millimeters operating at liquid nitrogen temperature and the corresponding joining technology is not easily available. We investigated the potential of additive manufacturing to fabricate hybrid plastic and ceramic structures of the insulating perovskite SrTiO3 together with the high- Tc superconductor YBa2Cu3O7, reaching a $T_{c}$ of up to 84 K in the 3D-printed polycrystalline materials. With our measurement setup, the structures are characterized in terms of $T_{c}$ and $I_{c}$ . With the successful process, now larger sample sizes and arbitrary hybrid structures can be manufactured. A gradiometric pick-up loop was fabricated and characterized. These structures can be integrated in low-noise plastic holders and encapsulated by plastic-printed capsules to protect the HTS devices from humidity. By additive manufacturing very versatile ceramic HTS multimaterial hybrid modules can be employed for novel HTS SQUID systems.

Elastic properties of HTSC ceramics

Elastic properties of ceramics of various high-temperature superconductor (HTSC) types are considered based on experimental data. The effect of porosity of HTSC ceramics is analyzed.

THE Y-HTSC RESISTIVE STATE DYNAMICS IN THE NON STATIONARY MAGNETIC FIELD

The paper carries out the research on the bulk ceramic high-temperature superconductors in resistive state and analyses two physical situations: dissipative motion of magnetic flux vortices throughout the whole sample, and localised in a thin near-surface layer. Hysteresis character of granular superconductor resistance in resistive state in case of change of external magnetic field has been detected. It is shown that a small alternating magnetic field ambiguously influences the resistance of HTSC in resistive state depending on the frequency due to the redistribution of magnetic flux vortices from weak pinning centres (from intergranular medium) to stronger centres (to granules).

Vibration converter with magnetic levitation

The paper presents a mathematical model, the results of computational and theoretical research, and the feasibility of creating a vibration converter with full magnetic levitation in the suspension of a high-temperature superconductor (HTSC). The axial and radial stability of the active part of the converter is provided by the interaction of the magnetic field of ring-shaped permanent magnets and a hollow cylinder made of the ceramic HTSC material. The force is created by a system of current-carrying coils whose magnetic field is polarized by permanent magnets and interacts with induced currents in the superconducting cylinder. The case of transition to the superconducting state of HTSC material in the field of the permanent magnets (FC mode) is considered. The data confirm the outlook for the proposed technical solutions.

Layering fabrication, structure, and electromagnetic properties of perovskite phases by hybrid process: self-propagated high-temperature synthesis and selective laser sintering

The paper discusses the fundamentals and the requirements for layer-by-layer manufacturing of three-dimensional porous parts from complex metal oxide systems (piezoceramics PbTi1−xZrxO3; hexaferrites – BaFe12−xCrxO19 and SrFe12O19; spinels – Li0.5Fe2.5−xCrxO4 and high-temperature superconducting ceramics (HTSC) – YBa2Cu3O7−y) and examines the main aspects of the overlapped processes associated with the self-propagated high-temperature synthesis (SHS) and selective laser sintering (SLS). These two techniques presently offered are joined as the original solutions in this external magnetic field. The perovskite phase compositions, morphology, and element distribution of the fabricated samples were analyzed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped the EDX analysis. Optimal regimes for the three-dimensional (3D) parts laser synthesis and some of their electro physical properties were estimated for conducting the concurrent SHS-SLS reactions, both for the case with the applied dc magnetic field and without it.

Gamma irradiation effects on EuBa2Cu3O7 high temperature superconductor

The Eu1Ba2Cu3O7 superconductor are synthesized using the solid state reaction method. The effect of gamma irradiation on transport properties and kinetic parameters of high-temperature ceramic Eu1Ba2Cu3O7 superconductor has been investigated. The bulk samples, prepared by the standard solid state reaction method, were irradiated by gamma rays of different doses in the range 0–30kGy at room temperature. Structure characterization using X-ray diffraction shows that decrease in the peak intensity represents a reduction in the content of the superconducting phase. The resistivity measurements are performed using the four-probe method in the temperature range from 77 to 300K. The changes in transition temperature show that Tc is very sensitive to gamma irradiation. The effects of irradiation on surface morphology have been investigated by scanning electron microscopy. The kinetic parameters have been estimated by thermogravimetric analysis.

Nonmonotonic structural changes in HTSC Bi-2201 ceramics depending on oxygen nonstoichiometry

Effect of the oxygen content in ceramic high-temperature superconductors Bi2Sr2CuO6 + δ on their phase composition, crystal structure, and charge state of cations has been studied. As the oxygen content changes, the lattice parameters were shown to exhibit nonmonotonic variation; no changes in the phase composition and charge state of cations take place. According to neutron diffraction data, the overstoichiometric oxygen atoms are introduced only into the BiO1 + δ layers. The nonmonotonic variations observed are explained assuming that, at a certain oxygen content, the hole charge carriers induced by introduced oxygen are localized in the BiO1 + δ layers rather than “flow down” into superconducting CuO2 layers.

Effect of Nanosize MgO Addition on the Texture and Mechanical Strength of Bi-2212 Superconductor Compound

The Bi2Sr2CaCu2O8 (Bi-2212) high-temperature ceramic superconductor has the potential to be applied in power system applications due to its low thermal conductivity. However due to the material’s brittle nature and low strength, reinforcement of the Bi-2212 superconductor is necessary for such applications. Due to its high melting point and lower heat capacity, magnesium oxide (MgO) is an excellent candidate as the reinforcement material. In this study, 3% to 8% weight percentage of nanosize MgO powder was added to Bi-2212 superconductor. The Bi-2212/MgO compounds were palletized and heat treated, followed by partial melting and slow-cooling. X-ray diffraction (XRD) was used to study the phases present in the samples. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDAX) analysis was performed to investigate the microstructure, and for identifying the elemental composition of the samples. Electrical resistance and critical current density (Jc) measurements were carried out using the standard four-probe dc method. The degree of texturing of the microstructure was determined using the texture coefficient calculations. In addition, the mechanical strength of the samples was studied by conducting compression test. The results show that the addition of small amount of MgO particles has improved the texture of the Bi-2212/MgO compound. The compound with 5% MgO addition shows significantly higher strength. Addition of higher than 8% of MgO has resulted in highly porous microstructure and subsequently decreasing the strength of the Bi-2212/MgO compound.

Nanostructured A<sub>2</sub>(RE,B)O<sub>6</sub> (A = Ba, Sr; RE = Rare-Earth; B = Sb, Zr) Perovskite Ceramics and their Potential Applications in Microwave and Superconducting Electronics

A group of perovskites with general formula A2(RE,B)O6(A=Ba, Sr; RE=Rare-Earth; B=Sb, Zr) were synthesized as nanocrystals owing to the enhanced specific surface area that nanomaterials posses. These perovskites are characterized by varied crystal structure depends on the relative sizes of the cations occupying the A and B sites of the perovskite lattice. The new materials were either insulators or semiconductors. They possess moderate dielectric constant (~30) and relatively low dielectric loss (10-4); and therefore, they could be used as substrates in microwave circuits. Some of them falls to the semiconducting range with band gap ~3.3 eV; and therefore, could be used as transparent wide band gap semiconductors. Furthermore, the new perovskites were found to be chemically stable with two mostly considered high temperature ceramic superconductors for practical applications, viz. YBa2Cu3O7-δ(YBCO) and (Bi,Pb)2Sr2Ca2Cu3Ox(BSCCO).

The effect of gamma irradiation on polycrystalline Y3Ba5Cu8O18

The effect of gamma irradiation on transport properties and kinetic parameters of high-temperature ceramic Y3Ba5Cu8O18 superconductor has been investigated. The bulk samples, prepared by the standard solid-state reaction method, were irradiated by gamma rays of different doses in the range 0–44.8 kGy at room temperature. The changes in transition temperature (T c ) and excess conductivity have been discussed. The effects of irradiation on surface morphology have been investigated by scanning electron microscopy. The kinetic parameters have been estimated by thermogravimetric analysis.

An Approach of the Sintering YBa2Cu3O7−δ System

The abnormal glow discharge applied to the sintering process is a recent technique used for processing both metallic and ceramic materials. In this paper, we use the abnormal glow discharge as an alternative method for the sintering step of the YBa2Cu3O7−δ superconductor material. The physical properties of the sintered samples by glow discharge were compared with the properties of sintered samples in resistive furnace, which is commonly used for production of high temperature superconductor ceramics. The structural analysis of the YBa2Cu3O7−δ samples was carried out by the X-ray diffraction technique, microstructural analysis by Scanning Electron Microscopy and electrical resistivity by the four probes method (resistance measurements as a function of temperature). The experimental results permitted to establish the similar structure and morphology for all samples: produced by plasma and resistive furnace sintering. The superconducting behavior was corroborated for both sintering processes.

Effect of the rotation of an external magnetic field on the internal flux distribution in superconducting ceramics: Experiments with polarized neutrons

The behavior of a magnetic flux in a ceramic high-temperature superconductor with rotation of a magnetic field through a specified angle has been investigated using polarized neutrons. Two models of penetration of a weak magnetic field into a granular superconductor have been discussed. Based on the obtained distributions of the rotation angle and the magnitude of the magnetic field inside the sample, the choice is made in favor of one of these models.

Acoustic emission from YBa2Cu3Ox superconductors

Yttrium-based high-temperature ceramic superconductors were prepared by the use ofa conventional solid state reaction. The common superconducting properties,critical temperature and critical current at 77 K, were determined by electricalmeasurements. The acoustic emission from the superconducting samples wasmeasured during the phase transition from the superconducting state to the normalstate following a temperature rise from 77 to 100 K. The rate and the sum ofthe ultrasound pulses are presented. Correlations were noticed between acousticemission and the superconducting parameters and superconducting state of thesamples. No emission was detected during the electrical current rise up to the criticalvalue.

Percolative theories of strongly disordered ceramic high-temperature superconductors

Optimally doped ceramic superconductors (cuprates, pnictides, etc.) exhibit transition temperatures T(c) much larger than strongly coupled metallic superconductors like Pb (T(c) = 7.2 K, E(g)/kT(c) = 4.5) and exhibit many universal features that appear to contradict the Bardeen, Cooper, and Schrieffer theory of superconductivity based on attractive electron-phonon pairing interactions. These complex materials are strongly disordered and contain several competing nanophases that cannot be described effectively by parameterized Hamiltonian models, yet their phase diagrams also exhibit many universal features in both the normal and superconductive states. Here we review the rapidly growing body of experimental results that suggest that these anomalously universal features are the result of marginal stabilities of the ceramic electronic and lattice structures. These dual marginal stabilities favor both electronic percolation of a dopant network and rigidity percolation of the deformed lattice network. This "double percolation" model has previously explained many features of the normal-state transport properties of these materials and is the only theory that has successfully predicted strict lowest upper bounds for T(c) in the cuprate and pnictide families. Here it is extended to include Coulomb correlations and percolative band narrowing, as well as an angular energy gap equation, which rationalizes angularly averaged gap/T(c) ratios, and shows that these are similar to those of conventional strongly coupled superconductors.