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Öğe Ac Susceptibility measurements and mechanical performance of Bulk MgB2(Springer, 2015) Öztürk, Özgür; Aşıkuzun, Elif; Kaya, Şeydanur; Erdem, Murat; Safran, Serap; Kılıç,Ahmet; Terzioğlu, CabirThe effects of Ar ambient pressure (vacuum and 0, 10, and 20 B) and annealing times (0.5 and 1 h) on microstructural, superconducting, and mechanical properties of bulk superconducting MgB2 are investigated. The samples are produced using the solid-state reaction method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements are performed for determination of the crystal structure and surface morphology of MgB2 samples, respectively. The superconducting properties are studied by AC magnetic susceptibility measurements. Microhardness analyses are made using the Vickers microhardness test for determination of mechanical properties of all samples. Increasing the Ar pressure decreases the lattice parameters and hence the average grain size. Increasing the annealing time results in larger lattice parameters and larger grain formation. The susceptibility measurements revealed a two-step transition which is reminiscent of granular superconductors. The intra-grain transition temperature is determined to be 38.4 K for all samples. The inter-grain transition temperature of 37.2 K is obtained for samples produced under Ar ambient pressure. The samples produced under Ar ambient pressure have better superconducting properties than the ones produced in vacuum. Increasing the annealing time under vacuum further decreases the superconducting properties probably due to Mg loss.Öğe Assessment of superconducting and structural stability of advanced Y-123 and Y-358 ceramics with Tb/Y substitution in main matrices(Elsevier Ltd, 2024) Güdücü, Gülnur; Öztürk, Özgür; Kurnaz, Sedat; Tokeşer, Elif Aşikuzun; Safran, Serap; Yıldırım, GürcanIn this study, the performances of Y1-x(Tb)xBa2Cu3O7-? (Y-123) and Y3-x(Tb)xBa5Cu8O18-? (Y-358) advanced ceramics prepared by sol-gel preparation route are investigated by the advanced characterization methods including X-ray diffraction (XRD), temperature dependent resistivity (?-T), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and energy distribution spectroscopy (EDS) measurements and theoretical approaches. The EDS results illustrated that the Tb impurities were replaced successfully by the yttrium sites in the YBa2Cu3O7-y main matrix. Similarly, it was noted that the presence of excess impurities in the crystal structure led to the oxygenation problems. Electrical properties were determined by temperature dependent resistivity (?-T) measurements. ?-T results indicated that Tb doping reduced the critical transition temperature (Tc) values for the transition to superconductivity for all samples in two YBCO phases. Although it appears to have negative effects of Tb ions on the number of mobile charge carrier concentrations in the ? antibonding in-plane Cu-O bonds, bipolaron formations in the polarizable lattices, oxidation states, and amplitude of the pair wave function of both phases, the other valuable properties (morphology, crystallinity quality, interaction between adjacent layers, critical current density, and flux pinning ability) were noted to improve remarkably in the case of the optimum amount in the Y-123 superconducting phase. In this context, the Y-358 superconducting phase was harshly affected by the substitution due to the change of the ortorombicity, localization problem, impurity phases, structure stabilization, crystal structure quality, crystallization system, homogeneities of oxidation states, oxygen ordering degree, and impurity scatterings. Besides, the analysis of the fluctuation induced conductivity indicated that the Y-123 ceramics with longer c-axis coherence length and less anisotropic nature exhibited well superconducting properties. Additionally, the doping ratio of x=0.01 led to the formation and distribution of more nucleation centers for the thermal fluxon motions of 2D pancake vortices. Similarly, the optimum Tb doped Y-123 system exhibited much durable to applied field strengths due to the best interaction quality between grains. Accordingly, this study recommended that the Y1-x(Tb)xBa2Cu3O7-? advanced ceramic structure with new functionalities can find much more application areas in innovative, heavy-industrial technologies, and advanced engineering-related sectors. © 2024 Elsevier B.V.Öğe Examination of pairing mechanism, orbital hybridization, stabilization and magnetization behavior of Tb/Y and Zn/Cu partially substituted Y-123 Superconductors(Elseiver Science SA, 2022) Öztürk, Özgür; Güdücü, G.; Safran, Serap; Yıldırım, GürcanThe effect of homovalent Tb/Y and Zn/Cu substitution on electrical, superconducting, structural, and magnetic features of Y-123 ceramic materials is extensively examined by powder X-ray diffraction, electrical resistivity, scanning electron microscopy, energy dispersive X-ray spectrometry, DC magnetization VSM measurements and related calculations. Y1-xTbxBa2Cu3O7-? and YBa2(Cu(1-x)Znx)(3)O(7-? )samples are prepared with four different molar percentages (0.0 <= x <= 0.15) using the sol-gel technique. DC magnetization data and the Bean model are used to evaluate change in critical current densities with an applied magnetic field. Energy-dispersive X-ray spectrometry measurements indicate that materials are exactly produced in the desired stoichiometric ratios. Moreover, all the experimental findings show that the fundamental characteristic properties are observed to decrease with replacement mechanism. The degradation mechanism with partial substitution is thoroughly explained scientifically in the basic contents for the first time. The role of Tb/Y and Zn/Cu partial substitution on the oxygen concentration level in unit cell, ordering degree in the Cu-O ribbons, lattice cell parameters, grain size, and the number of holes in the sigma antibonding in-plane Cu-O bonds are also discussed in detail. Additionally, beginning of weak-interaction problems between adjacent superconductive layers, formation of microscopic structural faults and decoupling of super-conducting grains are noted to be the negative effect of substitution mechanism. Regardless, it is observed that Tb-doped samples possessing more uniform surface morphologies with better surface texture and connection quality between particles show much higher magnetization behavior and superconducting properties. All in all, this study developing a scientific methodology about why fundamental characteristic features change with the partial replacements of Tb/Y and Zn/Cu in crystal systems seems a pioneering investigation to construct novel and feasible application fields for the Y-123 ceramic compounds. (C) 2022 Elsevier B.V. All rights reserved.Öğe Stabilization of durable tetragonal phase and barrier regions in y-123 ceramic systems with partial substitution mechanism(Springer, 2024) Guducu, Gulnur; Safran, Serap; Kurnaz, Sedat; Tokeser, Elif Asikuzun; Seydioglu, Turgay; Yildirim, Guercan; Ozturk, OzguerThis study examines the impact of Tb and Zn doping on the Y-123 superconducting system by analyzing crack propagation mechanisms through Vickers microhardness measurements. The measurements are conducted at various application forces ranging from 0.245 N to 2.940 N. The microhardness measurements are used to determine the role of impurity addition on Vickers hardness, modulus of elasticity, brittleness index, fracture toughness, and yield strengths. It is found that impurity ions serving as strong barrier regions improve the surface residual compressive stress sites and interactivity between the adjacent layers. Similarly, the sensitivity to the external forces reduce significantly with the substitution mechanism due to the induced new slip systems and ionic bond formations. Accordingly, all the mechanical performance properties are recorded to increase significantly with the impurity ions. Especially, the replacement of Zn by Cu ions in the Y-123 matrix exhibits higher resistance to failure, mechanical strength, and stabilization of the durable tetragonal phase. Accordingly, Zn/Cu substitution in Y-123 ceramics paves the way for the applications of ceramic compounds in the fields of heavy-industrial technology and industrial power systems. All the ceramic materials also exhibit indentation size effect feature based on the recovery mechanism. Additionally, load-independent microhardness parameters are semi-empirically modeled by Meyer's law, Hays-Kendall, indentation-induced cracking, elastic-plastic deformation, and proportional sample resistance model for the first time. According to the comparisons, the IIC model is identified as the most suitable for interpreting the real microhardness results of newly produced Y-123 ceramic matrices.Öğe Superconducting and mechanical properties of the bulk Si(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods(Elsevier, 2015) Safran, Serap; Kılıçarslan, Ebru Şimşek; Öztürk, Hamit; Alp, Meryem; Akdoğan, MustafaWe have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi185Pb0.35Sr2Ca2Cu3O10 (+/-) (y) stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness Lest. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (B-i, fracture toughness (K-IC) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters or materials. (C) 2015 Elsevier EN. All rights reserved.
