Papers by Keyword: YBCO

Abstract: Electron backscatter diffraction (EBSD) conventionally necessitates the preparation of flat, damage-free surfaces, typically achieved through mechanical or chemical polishing. However, for porous materials susceptible to fracture, such procedures are not only technically challenging but also risk altering or obscuring critical microstructural features, particularly at fine length scales. Despite the widespread reliance on surface polishing, its necessity in EBSD analysis—especially for highly porous materials—has seldom been critically examined, and studies omitting such preparation remain scarce. In the present study, EBSD analysis was conducted on porous polycrystalline YBa₂Cu₃O_y without any surface treatment. The absence of polishing preserved the pristine microstructure, free from artifacts commonly introduced by conventional preparation techniques. Although the surface topography limited the number of pixels yielding high-quality diffraction patterns, orientation imaging revealed that the surface granules predominantly exhibit single-crystalline domain structures. These findings demonstrate that EBSD can be successfully applied to porous materials without surface polishing, thereby providing a rapid, non-destructive approach for microstructural characterization while preserving the material’s intrinsic structural integrity.

Abstract: This work analyzes the lattice, electronic structures and hole concentration of calcium-doped YBCO compounds using density functional theory. The investigation was conducted on two models, Y_0.875Ca_0.125Ba₂Cu₃O₇ (YCa123) and Y_0.875Ca_0.125Ba₂Cu₄O₈ (YCa124), using density functional theory. The results reveal that calcium substitution induces changes in the lattice structure, including a decrease in the lattice constant and a distortion of the Cu-O₂ plane. Furthermore, the electronic structure was also altered, leading to changes in the density of states above the Fermi level. The hole concentrations were also calculated and were found to be 0.19 and 0.16 for YCa123 and YCa124, respectively. These results indicate that the hole concentration of YCa124 is lower than that of YCa123, consistent with the parabolic curve relationship between hole concentration and superconducting transition temperature. The results suggest that Cu (2) atoms fluctuate between the states of Cu⁺ and Cu²⁺, which may be crucial for understanding electron-electron pairing mechanism. These results could aid in the development of more efficient and practical superconducting materials through targeted doping strategies.

Abstract: The article presents a study of the transport properties of high-temperature superconducting compounds of the Y-Ba-Cu-O system with the addition of the carbon nanomaterial (carbon nanotubes) "Taunite" in different concentrations. According to the data of X-ray phase analysis, scanning electron microscopy and magnetic measurements, it was determined that the carbon nanotube "Taunite" contains ferro-and superparamagnetic particles (~ 30 nm). The dependences of the resistance of the samples on the temperature have been constructed, and the temperature of the transition of the samples to the superconducting state (~ 90 K) has been determined, and the features ("stages") on the resistance curves are observed below. Nickel nanoparticles in the carbon nanotubes "Taunite" have been established to not affect the critical temperature of the superconducting transition, yet after reaching a certain concentration, they destroy the superconducting state.

Abstract: The article examines the effect of nickel nanoparticles on the magnetic properties of the YBCO superconductor. The ceramics were obtained by solid-phase synthesis using yttrium oxide, copper (II) oxide, and barium carbonate with the addition of carbon nanotubes "Taunite" of different concentrations (0, 20, 50, 70, 100 mg). Magnetic studies have demonstrated that ferromagnetism and superparamagnetism are both observed in the samples, which can be explained by the presence of nickel particles. The dependences of the magnetization in the applied magnetic field of the sample without the addition of the carbon nanotubes "Taunite" have a paramagnetic course, and their slope monotonically increased with decreasing temperature. The coercive force of the samples and the value of the magnetic moment has been determined to increase upon the decrease in temperature. The high homogeneity of the heterostructures has been demonstrated in the graphs of FC/ZFC explained by the uneven distribution of nickel nanoparticles, which do not integrate into the crystal lattice and, due to the long-range order of interaction, do not make a strong contribution to the magnetization.

Abstract: The effects of the multiforric BiFO₃ nanoparticles addition on the structure and superconducting properties of YBa₂Cu₃O_7–δ (Y123) with different concentrations were systematically investigated using X-ray diffraction (XRD), field emission scanning electron micrograph (FESEM), EDX and four point probe measurement. It was found that the added samples were predominant by Y-123 phase beside small amount of Y-211 and unreacted BiFeO3 secondary phases. Samples with less (wt.%) BFO added YBCO precursor powder preserved the orthorhombic structure similar to the pure YBCO, while samples with higher wt% addition show orthorhombic-to-tetragonal transition tendency. The samples became more porous and their grain size slightly decreased with addition of BiFeO₃. The addition of nanoBiFeO3 disturbed the grain growth of Y123, thus resulting in the degradation of superconducting properties of the samples. The superconducting transition temperature (Tc onset) of samples decreased from 92 K for x=0.0 to 44 K for x=10.0 wt. %, which could be attributable to oxygen vacancy disorder.

Abstract: Single grain YBCO bulk superconductors were prepared from different starting precursors. In the first case, Y₂Ba₁Cu₁O₅ (Y211) powder as the solid phase and the liquid phase of mixture of YBa₂Cu₃O_7-x+BaCuO₂+CuO powders were used. In the second case the solid phase was prepared from the mixture of Y₂O₃+BaCuO₂ instead of the conventionally used Y211. The microstructure of samples was studied by polarized light microscopy and scanning electron microscope (SEM). The influence of different staring compositions on the final size of Y211 particles is shown. Also the influence of BaCuO₂ concentration in the Y₂O₃+x·BaCuO₂ (x=0.2; 0.5; 0.8; 1; 1.2; 1.5; 1.8) mixture on the Y211 size was studied.

Abstract: The effect of Ca substitution on the electrical and structural properties in high and low density Y(Ba_1-xCa_x)₂Cu₃O_δ where x = 0.00, 0.10, 0.20 and 0.30 via solid state reaction method has been investigated. The electrical properties, elemental analysis, and structural identification were measured by the four-point probe technique, energy dispersive x-ray (EDX) and X-ray diffraction (XRD) respectively. The electrical properties such as critical temperature (T_c) and critical current density (J_c) were found to be strongly dependent in both high and low densities Y(Ba_1-xCa_x)₂Cu₃O_7-δ. These parameters were decreased monotonously with the increasing of Ca substitution. An obvious results of the Ca-doped samples can be seen in x = 0.20 where T_{c zero} of high density sample is 77 K, which is higher than that of the low density sample that occurred at 73 K. Meanwhile, J_c at 60 K for high density is 1.842 A/cm² compared to 1.410 A/cm² in low density sample. EDX analysis confirmed the existence of Ca in all doped samples. The crystallographic structure remained orthorhombic and the volume of unit cell increased towards further increased of Ca concentration.

Abstract: In this work, we analyze the electronic structure and charge distribution of the YBCO family compounds Y-123 and Y-124 bulk using the density functional theory. The band structures and the density of states of the compounds are shown. The charge transfers between the atoms in the two compounds are compared and discussed in detail. The lattice parameters obtained by Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm are compared with the experimental parameters. The critical differences of the charge distribution for these two compounds are discussed.

Abstract: YBa₂Cu₄O₈ has emerged as better choice in superconducting application thank to it strong thermal stability. High pressure techniques had been employed for the preparation of YBa₂Cu₄O₈ but it might costly and/or inconvenient. Several research groups had showed that the YBa₂Cu₄O₈ can also be prepared by conventional solid state method with heating at 1 atm oxygen pressure; however the phase formation processes are yet brief and clear. This work infiltrated the phase formation processes in preparing the YBa₂Cu₄O₈ under solid state method with heating at 1 atm oxygen pressure. The effectiveness of the use of sodium nitrate as an enhancer was brought to light by the experiment results. Significant YBa₂Cu₄O₈ phases were successfully synthesized.

Abstract: This paper reports on the properties of YBa₂Cu₃O_d (Y123) and YCaBa₄Cu₆Oy (Y146) with non-porous and porous structures. The relationship between calcium doping and critical temperature (T_c) was studied to determine the optimal superconducting properties. A series of heating and grinding via solid state reaction method was used to fabricate the ceramic materials. The electrical properties were investigated via critical temperature, T_C and critical current density, J_C using the resistivity measurement system (RMS). Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) were used to analyze the material morphology and structure, respectively. The orthorhombicity increased due to less porosity of the samples. The calcium presence partially replaced larger Ba(II) site and degraded orthorhombicity. The highest critical current density (J_C) was porous YCaBa₂Cu₃Oy which was 2.32 A/cm² compared to 0.75 A/cm² for porous YCaBa₄Cu₆Oy at 60 K. The critical temperature for porous structure was less than non porous structure for Ca doped Y146 system which was 69.9 K and 67.9 K. SEM micrograph unveiled that the Jc was induced significantly by continuity of grain formation via grain size. Pores homogenized the grains surface quality and connectivity due to strain release thus increasing effective cross section of the sample for current density (Jc) over the vast areas.