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    Change in transition balance between durable tetragonal phase and stress-induced phase of cobalt surface-layered in Bi-2212 materials by semi-empirical mechanical models
    (Iop Publishing Ltd, 2023) Erdem, Umit; Yildirim, Gurcan; Turkoz, Mustafa Burak; Ulgen, Asaf Tolga; Mercan, Ali
    This study has indicated the positive effect of sintering temperature on the mechanical durability, strength, critical stress, deformation degrees, durable tetragonal phase, failure and fracture by fatigue, and mechanical characteristic behavior to the applied test loads for the Co surface-layered Bi-2212 ceramic materials produced by the standard solid-state reaction method. The sintering mechanism has been used as the driving force for the penetration of cobalt ions in the Bi-2212 ceramic matrix. The microindentation hardness test measurements have been performed at the load intervals 0.245 N-2.940 N. The experimental findings have also been examined by the six different semi-empirical mechanical and indentation-induced cracking models. It has been found that all the mechanical performance parameters are improved considerably with increasing the diffusion sintering temperature up to 650 degrees C. On this basis, the Co surface-layered Bi-2212 sample produced at the sintering temperature of 650 degrees C has been observed to improve dramatically the mechanical durability and resistance to the applied test loads as a consequence of the formation of new force barrier regions, surface residual compressive stress regions, and slip systems in the Bi-2212 ceramic system. Similarly, the optimum sintering temperature has extensively enhanced the elastic recovery mechanism, critical stress values, and deformation degree levels, stored internal strain, and crack surface energy through the Bi-2212 ceramic materials. Accordingly, it has been noted that the best sample produced at 650 degrees C is more hardly broken than the other ceramics. Namely, the optimum sintering temperature has decreased the sensitivity to the applied test loads as a result of delaying the beginning of the plateau limit regions. On the other hand, all the mechanism has been found to reverse completely depending on the excess sintering temperature. Lastly, the indentation-induced cracking model has been found to exhibit the closest results to the original Vickers microhardness parameters in the plateau limit regions.
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    Contribution of vanadium particles to thermal movement of correlated two-dimensional pancake Abrikosov vortices in Bi-2223 superconducting system
    (Elsevier, 2023) Ulgen, Asaf Tolga; Erdem, Umit; Yildirim, Gurcan; Turkoz, Mustafa Burak; Turgay, Tahsin
    This article breaks new ground in understanding of variation in the magnetic strength performance, flux pinning and energy dissipation mechanism of polycrystalline bulk Bi1.8Sr2.0Ca2.2Cu3.0Oy (Bi-2223) superconducting materials added with the different vanadium concentration level (0.0 <= x <= 0.30) under the magnetic field strengths applied up to 5 T for the first time. We provide the sophisticated and phenomenological discussions on the magnetoresistivity measurement results in three main sections along the paper. All the findings show that the increase of both the vanadium concentration in the crystal structure and external magnetic field strength damages significantly the magnetic strength performance, vortex dynamics, flux pinning ability and vortex lattice elasticity of bulk Bi-2223 superconducting ceramics. The vanadium addition promotes thermally the movement of correlated two-dimensional (2D) pancake Abrikosov vortices between the in-plane Cu-O-2 layers in the valance band, vortex lattice elasticity, vortex dynamics, distance for interlayer Josephson couplings and flux pinning centers and the theoretical computations confirm the remarkable degradation in the formation of super-electrons in the Bi-2223 crystal system. Thus, the vanadium addition is anticipated to be one of the best selectable materials to examine the differentiation in the thermal movement of correlated 2D Pancake Abrikosov vortices in the bulk Bi-2223 superconducting system. (c) 2022 The Author(s). Published by Elsevier Espana, S.L.U. on behalf of SECV. This is anopen access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).
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    Development of modulation, pairing mechanism, and slip system with optimum vanadium substitution at Bi-sites in Bi-2212 ceramic structure
    (Elsevier Science Sa, 2023) Ulgen, Asaf Tolga; Okur, Semih; Erdem, Umit; Terzioglu, Cabir; Turgay, Tahsin; Turkoz, Mustafa Burak; Yildirim, Gurcan
    Present study focuses extensively on the change in electrical, superconducting and microhardness parameters with partial substitution of trivalent V+3 impurities replacing Bi+3 ions in Bi-2212 ceramic compound with the aid of dc electrical resistivity and microhardness test measurements. Experimental findings, calculation results, and phenomenological discussions provide that the optimum vanadium substitution level is found to be x = 0.01 in the Bi2.0-xVxSr2.0Ca1.1Cu2.0Oy (Bi-2212) ceramic system for the highest conductivity, crystallinity quality, superconducting, and mechanical performance features depending on the decreased microscopic structural problems. All the findings are wholly verified by scanning electron microscopy (SEM) and X-Ray diffraction (XRD) analyses. The dc electrical measurements indicate that the optimum vanadium ions support the pairing mechanism for the formation of new polaronic states in the clusters of microdomains, and hence expand superconducting energy gap due to the enhancement of amplitude part of pair wave function in the spin-density wave systems. The excess vanadium content degrades all the basic thermodynamics and quantum mechanical quantities mentioned due to the stress-induced phase transformation. Numerically, the Bi-2212 advanced ceramic matrix prepared by the optimum vanadium impurity is noticed to present the smallest residual resistivity value of 0.08 m & omega; cm, room temperature resistivity value of 8.84 m & omega; cm, and broadening degree of 0.36 K. Similarly, the ceramic material is found to possess the highest residual resistivity ratio of 3.05, carrier concen-tration number of 0.153041, critical transition offset and onset value of 84.66 K and 85.02 K, respectively. Besides, the microhardness findings reveal that the same compound with the least sensitivity to the applied test loads exhibits the largest Hv value of 4.799 GPa, Young's moduli of 393.303 GPa, yield strength of (0.969 GPa), and elastic stiffness coefficient of 15.5574 (GPa)7/4 under the applied test load of 0.245 N. The XRD in-vestigations show that the presence of optimum vanadium impurity supports the formation of a high super-conducting phase, c-axis length, and average crystallite size. All the findings are morphologically confirmed by the SEM images. It is found that the crystallographically best crystallinity quality and view of surface morphology is observed for the optimum vanadium substitution level. All in all, new higher properties for the conductivity, crystallinity quality, surface morphology, superconducting, and microhardness parameters based on the optimum vanadium replacement encourage the Bi-2212 crystal system to use in much more application places.
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    Evolution of residual compressive stress regions in Co-diffused Bi-2212 engineering ceramics with annealing temperature
    (Springer, 2024) Mercan, Ali; Erdem, Umit; Ulgen, Asaf Tolga; Gulen, Mahir; Turkoz, Mustafa Burak; Turgay, Tahsin; Yildirim, Gurcan
    The role of diffusion annealing temperatures intervals 600-850 degrees C on durable tetragonal phase, surface morphology, and main mechanical performance parameters of Co surface-layered Bi2.1Sr2.0Ca1.1Cu2.0Oy (Bi-2212) samples has extensively been examined by scanning electron microscopy (SEM), Electron Dispersive X-ray (EDX) technique and microindentation Vickers hardness (Hv) tests. The experimental findings have shown that every material prepared has presented different composition distributions on the specimen surface as a consequence of the successful production of materials. Besides, the mechanical characteristics and durable tetragonal phase have been noted to enhance significantly with the enhancement of annealing temperature up to 650 degrees C due to the formation of new slip systems, surface residual compressive stress regions, connections between grains, and chemical bonding between the foreign and host atoms. Further, the optimum temperature has led to the reduction in stored internal strain energy and degree of granularity in the Co-diffused Bi-2212 crystal system. In this respect, the sample with the least sensitive to the external forces has exhibited the highest elastic modulus of 0.5445 GPa, shear modulus of 17.8515 GPa, yield strength of 181.5 MPa, and resilience of 369.1 MPa under 0.295 N. Accordingly, the cracks and dislocations have preferred to propagate throughout the transcrystalline regions, and crack growth size was easily controlled. Similarly, the saturation limit region has begun at relatively higher applied test load magnitudes. Conversely, the excess annealing temperature has caused the increase in the agglomeration of cobalt ions throughout the intergranular regions. Correspondingly, the activation of stress-induced phase transformation has been triggered seriously. Bi-2212 ceramic compound exposed to the optimum diffusion annealing temperature exhibits the most uniform surface view and crystalline quality with the densest surface morphology and the largest particle distributions and orientations. Moreover, every material studied has perfectly presented the characteristic indentation size effect behavior. The examination of granularity degree depending on elasticity moduli has verified all the Hv test results and discussions. All in all, this study guides the use of engineering ceramics in more application areas due to the increase in their service life.
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    Variation of fundamental features of cobalt surface-layered Bi-2212 superconductor materials with diffusion annealing temperature
    (Elsevier Sci Ltd, 2023) Oz, Ilker; Terzioglu, Cabir; Oz, Muhammed; Ulgen, Asaf Tolga; Turkoz, Mustafa Burak; Erdem, Umit; Yildirim, Gurcan
    The present study appears extensively on the role of diffusion annealing temperature intervals 650-850 degrees C on electrical conductivity, flux pinning ability, superconducting and crystallinity quality of Cobalt (Co) surface -layered Bi-2212 compounds with experimental tests including dc resistivity, bulk density, X-ray diffraction, critical current density measurements, and theoretical calculations. Experimental findings display that the Co ions may be replaced mostly by bismuth sites in the crystal lattice as a consequence of appropriate cation -vacancy, electron configurations of the outer shell, chemical valence states, and electronegativity of chemical contents in the main composition. The fundamental characteristic features refine considerably with 650 degrees C annealing temperature due to enhancement of antiferromagnetic spin fluctuations in the clusters of micro -domains, re-ordering of Cu-O bonds, stabilization of system, pairing mechanism, modulation of insulating Bi-O double layers, and orbital hybridization mechanisms. Accordingly, bulk Bi-2212 ceramic obtained at optimum annealing temperature exhibits the best conductivity because of a decrease in systematic crystallinity problems and potential grain boundary interaction problems expected in the system. Likewise, the optimum annealing temperature triggers the artificial nucleation regions for 2D discrete pancakelike Abrikosov vortices to decelerate thermal fluxon movements. Moreover, the X-ray diffraction results indicate that optimum Co ions in crystal lattice significantly improve crystal structure quality, grain alignment distributions in c-axis orientation, the extension of high-Tc Bi-2223 superconducting phase, and average crystallite size parameters. Additionally, the nucleation activation energy is noticed to reduce with optimum Co ions due to enhancement in the nucleation stability and crystallization temperature values to higher temperature zones. Namely, optimum Co ions easily diffusing into the lattice points support the formation of surface nucleation. In contrast, after a critical value of 650 degrees C, the characteristic properties mentioned suppress remarkably. In conclusion, the main characteristic features are extensively improved by the optimum diffusion annealing temperature for usage in novel and feasible market areas.