Substitution of Sm at Ca site in superconductors

Öztürk, O.; Akdoğan, Mustafa; Aydin, H.; Yilmazlar, Mustafa; Terzioğlu, C.; Belenli, I.

doi:10.1016/j.physb.2007.05.028

Cited by 37 publications

(16 citation statements)

References 33 publications

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“…Several techniques [6][7][8][9][10][11][12][13][14] have widely been used to improve their superconducting properties for years. Rare-earth addition and substitution are the most commonly used techniques [15][16][17][18]. Nevertheless, these techniques may sometimes cause to decrease the number of charge carriers (either holes or electrons) in the sample because of the replacement of Ca 2+ by more cationic ions; hence, the density of mobile holes in the CuO 2 planes decreases and the superconductivity degrades [6,19,20].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Structural and Superconducting Properties of Cr Added Bi-2212 Superconducting Ceramics

Yıldırım

Yücel

Bal

et al. 2011

J Supercond Nov Magn

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This study reports the effect of Cr addition on the structural and superconducting properties of Bi 1.8 Sr 2.0 Crx Ca 1.1 Cu 2.1 O y superconductor with x = 0, 0.1, 0.3, 0.5 0.7, and 1 by means of X-ray analysis (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and resistivity measurements. The samples studied in this work were prepared using the standard solid-state reaction method. Zero resistivity transition temperatures (T c ) are qualitatively estimated from the dc resistivity measurements. The zero resistivity transition temperatures are obtained to decrease from 81 K to 53 K with the increase in Cr addition. Moreover, the phase and lattice parameters were determined from XRD measurements. Based on the refinement of cell parameters done by considering the structural modulation, the Cr addition was confirmed by an increase of the lattice parameter a and decrease of the cell parameter a of the samples in comparison with that of the undoped sample (Cr0). As for the microstructure and element composition analyses on the surface of the samples produced, SEM and EDS measurements were investigated. According to the measurements, not only were the grain sizes of the samples noted to decrease, but also the surface morphology and grain connectivity were obtained to degrade with increase in the

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Section: Introductionmentioning

confidence: 99%

Investigation of Structural and Superconducting Properties of Cr Added Bi-2212 Superconducting Ceramics

Yıldırım

Yücel

Bal

et al. 2011

J Supercond Nov Magn

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“…The first one is attributed to the partial substitution of larger ionic radius of Ca 2+ ion, 0.990 Å, by the smaller one of Ho 3+ ion, 0.901 Å, at the same 6-fold coordination type [45]. The second reason is that the partial substitution of Ca 2+ ions by Ho 3+ ions leads to an increase in the oxygen content of the unit cell that enhances the average oxidation state, leading to smaller Cu-O distance within the copper-oxygen sheets [46]. In addition, the lattice parameter a is controlled by the length of the in-plane Cu-O bond which may be expanded as a result of electron addition into anti-bonding orbital through the partial substitution of Ca 2+ ions by Ho 3+ ions [47].…”

Section: Characterization and Investigationmentioning

confidence: 99%

Electrical and mechanical properties of (Bi,Pb)-2223 substituted by holmium

et al. 2016

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Abstract:The effect of the partial substitution of Ca 2+ by Ho 3+ ions on the electrical and mechanical properties of the superconducting phase (Bi,Pb)-2223 was studied. Superconducting samples of the type (Bi 1.8 Pb 0.4 )Sr 2 Ca 2.1−x Ho x Cu 3.1 O 10+δ were prepared by solid-state reaction technique under ambient pressure, and characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The superconducting transition temperature T c and pseudogap temperature T * were estimated from electrical resistivity measurements, while the critical current density J c was determined from I-V curves. The electrical resistivity data were discussed according to bipolaron model in the absence of thermally excited individual polarons. The sample with x = 0.025 showed the highest phase volume fraction, T c , and J c . Room temperature Vickers microhardness measurements were carried out at different applied loads (0.25-5 N) in order to investigate the performance of the mechanical properties of (Bi 1.8 Pb 0.4 )Sr 2 Ca 2.1−x Ho x Cu 3.1 O 10+δ phase. It was found that all the samples exhibit normal indentation size effect (ISE). The Vickers microhardness number H V increased as x increased from 0 to 0.025. The experimental results were discussed in view of Meyer's law, Hays-Kendall (HK) approach, elastic/plastic deformation (EPD) model, and proportional specimen resistance (PSR) model. The load independent (true) microhardness of (Bi 1.8 Pb 0.4 )Sr 2 Ca 2.1−x Ho x Cu 3.1 O 10+δ superconducting samples showed identical behavior to that of the PSR model.

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“…The increase of the transition width and appearance of double-step behaviour indicate that the KMnO 4 -added samples have a greater number of grain boundaries because the double-step resistive transition is an indication of weak links. 17,18 It is well-known that substitutions on the Cu sites have a very strong effect on the superconducting properties. In particular, the electronic configuration of the system is destroyed by the substitution of KMnO 4 for Cu 2+ , causing the reduction of the electronic conductivity in the CuO planes through the formation of impurity bonds.…”

Section: Electrical Resistance (Dc) Measurementsmentioning

confidence: 99%