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Journal ArticleDOI

Effect of melting time on the superconductivity in Bi1.7Pb0.3Sr2CaCu2O8 superconducting system

A. Sedky1
11 Jun 2010-Journal of Alloys and Compounds (Elsevier)-Vol. 499, Iss: 2, pp 238-242
TL;DR: In this article, the effect of melting time (1.5-5min+5 s) in air and at 920-°C on the normal and superconducting properties of Bi1.7Pb0.3Sr2CaCu2O8 (Bi (Pb): 2212) system was reported.
About: This article is published in Journal of Alloys and Compounds.The article was published on 2010-06-11. It has received 4 citations till now. The article focuses on the topics: Residual resistivity & Electrical resistivity and conductivity.
Citations
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Journal ArticleDOI
TL;DR: In this article, structural, mechanical and superconducting properties of Bi2Sr2Ca1−xYxCu2Oy superconductors with various x values (0.00≤x≤0.50) are investigated by X-ray diffraction, scanning electron microscopy, Vickers hardness and resistivity measurements.
Abstract: Structural, mechanical and superconducting properties of Bi2Sr2Ca1−xYxCu2Oy superconductors with various x values (0.00≤x≤0.50) are investigated by X-ray diffraction, scanning electron microscopy, Vickers hardness and resistivity measurements. It is found that the replacement of Ca2+ by Y3+ does not influence the phase purity of Bi:2212 while lattice parameters, orthorhombic distortion, surface morphology, oxygen content and hole carrier per Cu ion (P) are affected. Furthermore, the critical temperatures Tc are increased by increasing Y content up to 0.30, followed by a decrease with further increase of Y content up to 0.50. The values of Tc are 88, 94, 101, 104 and 50° K for x=0.00, 0.075, 0.15, 0.30 and 0.50, respectively. Similar behavior is obtained for the absolute values of true hardness Ht and surface energy γ against Y content while the opposite behavior is recorded for the hole carrier per Cu ion (P), deduced from Tc values, against Y content. Similar behavior is obtained for the absolute values of true hardness Ht and surface energy γ against Y content. These results are discussed in terms of possible reasons for suppression of superconductivity by Y substitution at the Ca site in the Bi:2212 superconducting system.

20 citations

Journal ArticleDOI
TL;DR: In this article, the normal and superconducting properties of Bi1.7Pb0.30Sr2Ca2−xLaxCu2Oy (Bi, Pb):2223 system with various x values (0.00, 0.30) have been reported.
Abstract: The normal and superconducting properties of Bi1.7Pb0.30Sr2Ca2−xLaxCu2Oy (Bi, Pb):2223 system with various x values (0.00 ≤ x ≤ 0.30) have been reported. It is found that the replacement of Ca2+ by La3+ up to 0.30 does not influence the phase purity of the pure system, while the orthorhombic distortion, excess oxygen, effective Cu valance and hole carriers/Cu ions are clearly affected. Further, the doping distance and crystal geometry factor are decreased, but the distance between neighboring Cu-atoms and density of excess doping are increased. Furthermore, the DTA diagrams show strong endothermic peaks Tm at 844.1, 848, 850.1 and 857.4 °C for pure and La samples, respectively. The mass loss determined by TGA displayed a sharp mass loss started at about 800 °C and extended to 1000 °C for all samples. Although the critical temperatures Tc of the samples are decreased by La insertion from 119 to 104, 71, and 53 K, the critical concentration for quenching superconductivity may be extended above 0.30. On the other hand, the Vickers hardness Hv is increased by La up to 0.30, but it is decreased by the applied load F. Additionally, a negative linear relation between Tm or HV and Tc is obtained as due to cooperative interactions, (Tc ∝ –Tm) i.e. there are an extended forces acting along such a wide temperature range. The Hv–F characters are divided into two linear parts; the first at lower loads (0.00–1.96 N) and the second at higher loads (2.94–4.90 N). The variation of surface energy ϒ against La is different according to the range of applied loads, while the elastic indentation de is decreased, and the resistance pressure Fo is increased. But, the values of Fo and de at higher loads are generally more than that of lower loads, while the vice is versa for the ϒ. Our results are discussed in terms of the balance between the hole carriers lost by La3+ with that introduced by excess oxygen in the Cu–O2 planes.

7 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of melting time on conductivity and dimensionality of BSCCO cooper oxide system was investigated and it was found that the mean field and crossover temperatures (Tcmf, T01, T02, and T03) are increased by increasing tm up to 35 min, followed by a decrease with further increase up to 45 min The logarithmic plots of excess conductivity (∆σ) and reduced temperature (Є) reveal three regions of different exponents corresponding to two crossover temperatures in the slope of each plot.
Abstract: We report here the effect of melting time (tm = 25–45 min) on the conductivity and dimensionality of BSCCO cooper oxide system It is found that the mean field and crossover temperatures (Tcmf, T01, and T02) are increased by increasing tm up to 35 min, followed by a decrease with further increase of tm up to 45 min The logarithmic plots of excess conductivity (∆σ) and reduced temperature (Є) reveal three regions of different exponents corresponding to two crossover temperatures in the slope of each plot Interestingly, the crossover occurs from three dimensional (3D) to zero dimensional (0D/SW) in the mean field region and from 0D/SW to two dimensional (2D) in the critical field region, for the samples melted at tm = 25, 4, and 45 min, while it occurs from (3D) to one dimensional (1D) and from (1D) to (2D) for the sample melted at tm = 35 min On the other hand, we have estimated several physical parameters such as order parameter exponents (λ), interlayer coupling (K), c-axis coherence length (ξc (0)), anisotropy (γ), Ginsburg number (Gi), critical magnetic fields (Hc(0), Hc1(0), and Hc2(0)), and critical current (Jc (0)) for all samples It is found that λ1, λ3, K, ξc (0), Gi, and γ are increased by increasing tm up to 35 min, followed by a decrease with further increase of tm up to 45 min as well as Tc, Tcmf, and T0 behaviors But the vice is versa for the behaviors of λ2, κ, Hc(0), Hc1(0), Hc2(0), Jc(0), and NG Moreover, it is observed that the behavior of critical fields and critical current against melting time is controlled by the order parameter exponent of the second region rather than the first and third regions These results are discussed in terms of the correlation between the effects of melting time on the weak links and the flow of actual supercurrent in the considered system

6 citations

Journal ArticleDOI
TL;DR: In this paper, the structural and superconducting properties of Bi2Sr2CaY ≥ 0.00 ≤x≤ 0.50 were investigated using resistivity and ac susceptibility measurements.
Abstract: We report here the structural and superconducting properties of Bi2Sr2CaY x Cu2 O y superconductors with various x values (0.00 ≤x≤ 0.50) by using the resistivity and ac susceptibility measurements. It is found that addition of Y 3+ does not influence the phase purity of Bi:2212, while c-parameter and orthorhombic distortion are affected. Furthermore, the critical temperatures T c(R= 0) are increased from 92 K for Y = 0 up to 106 K by 0.15 of Y, followed by a decrease with increasing Y up to 0.50. It is interesting to note the resistivity of the samples with Y = 0.075 and 0.15 reaching to true zero value only at low dc currents up to 2 mA. Interestingly, the onset temperature of diamagnetism obtained from susceptibility data remains nearly unchanged at 94 K up to Y = 0.30, flowed by a decrease to 86 K at Y = 0.50. The superconducting volume fraction and critical currents are improved by Y addition up to 0.15, followed by a decrease with increasing Y up to 0.50. These results are explained in terms of the effects of excess oxygen, secondary phases, and carrier concentration per Cu ions which are produced by Y addition in Bi:2212 system.

1 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a new high-Tc oxide superconductor of the BiSrCa-Cu-O system without any rare earth element was discovered, which has Tc of about 105 K, higher than that of YBa2Cu3O7 by more than 10 K.
Abstract: We have discovered a new high-Tc oxide superconductor of the Bi-Sr-Ca-Cu-O system without any rare earth element. The oxide BiSrCaCu2Ox has Tc of about 105 K, higher than that of YBa2Cu3O7 by more than 10 K. In this oxide, the coexistence of Sr and Ca is necessary to obtain high Tc.

2,698 citations

Journal ArticleDOI
TL;DR: In this article, the spatial interrelationships between STM tunneling spectra in underdoped Bi2Sr2CaCu2O8+x were investigated and it was shown that the electronic structure can be divided into 3nm diameter domains with superconducting characteristics and local energy gap delta 50(2.5) meV.
Abstract: Granular superconductivity occurs when microscopic superconducting grains are separated by non-superconducting regions through which they communicate by Josephson tunneling to establish the macroscopic superconducting state [1]. Although crystals of the cuprate high-Tc superconductors are not granular in a structural sense, theory indicates that at low hole densities the holes can become concentrated at some locations resulting in hole-rich superconducting domains [2-5]. Granular superconductivity due to Josephson tunneling through 'undoped' regions between such domains would represent a new paradigm for the underdoped cuprates. Here we report studies of the spatial interrelationships between STM tunneling spectra in underdoped Bi2Sr2CaCu2O8+x. They reveal an apparent spatial segregation of the electronic structure into ~3nm diameter domains (with superconducting characteristics and local energy gap delta 50(2.5) meV. These observations suggest that underdoped Bi2Sr2CaCu2O8+x is a mixture of two different short-range electronic orders with the long-range characteristics of a granular superconductor.

583 citations

Journal ArticleDOI
24 Jan 2002-Nature
TL;DR: In this article, underdoped Bi2Sr2CaCu2O8+δ superconductors are shown to be a mixture of two different short-range electronic orders with the long-range characteristics of a granular superconductor.
Abstract: Granular superconductivity occurs when microscopic superconducting grains are separated by non-superconducting regions; Josephson tunnelling between the grains establishes the macroscopic superconducting state1. Although crystals of the copper oxide high-transition-temperature (high-Tc) superconductors are not granular in a structural sense, theory suggests that at low levels of hole doping the holes can become concentrated at certain locations resulting in hole-rich superconducting domains2,3,4,5. Granular superconductivity arising from tunnelling between such domains would represent a new view of the underdoped copper oxide superconductors. Here we report scanning tunnelling microscope studies of underdoped Bi2Sr2CaCu2O8+δ that reveal an apparent segregation of the electronic structure into superconducting domains that are ∼3 nm in size (and local energy gap 50 ± 2.5 meV. These observations suggest that underdoped Bi2Sr2CaCu2O8+δ is a mixture of two different short-range electronic orders with the long-range characteristics of a granular superconductor.

581 citations

Journal ArticleDOI
TL;DR: In this article, the effect of chemical inhomogeneities on the superconducting transition temperature was examined and it was shown that partial substitution of Sr by Ln (Ln = La, Pr, Nd, Sm, Eu, Gd, and Bi) results in a monotonic decrease of the transition temperature with increasing ionic radius mismatch.
Abstract: We examine the effect on the superconducting transition temperature ${(T}_{\mathrm{c}})$ of chemical inhomogeneities in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CuO}}_{6+\ensuremath{\delta}}$ and ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ single crystals. Cation disorder at the Sr crystallographic site is inherent in these materials and strongly affects the value of ${T}_{\mathrm{c}}.$ Partial substitution of Sr by Ln (Ln = La, Pr, Nd, Sm, Eu, Gd, and Bi) in ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{1.6}{\mathrm{Ln}}_{0.4}{\mathrm{CuO}}_{6+\ensuremath{\delta}}$ results in a monotonic decrease of ${T}_{\mathrm{c}}$ with increasing ionic radius mismatch. By minimizing Sr site disorder at the expense of Ca site disorder, we demonstrate that the ${T}_{\mathrm{c}}$ of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ can be increased to 96 K. Based on these results we discuss the effects of chemical inhomogeneity in other bulk high-temperature superconductors.

386 citations

Journal ArticleDOI
TL;DR: In this paper, the anomalous behavior of the Hall coefficients of R H has been studied over wide temperature regions, and the formation process of the abnormal metallic state of high-T c oxides at low temperatures has been elucidated.
Abstract: Transport properties of La 2- x Sr x CuO 4 , YBa 2 Cu 3 O 6+ x and Bi 1.6 Pb 0.5 Sr 1.9- y La y Cu 1.05 O z have been studied over wide temperature regions. Drastic temperature variations of the Hall coefficients R H found in the underdoped region of the hole carriers suggest that there exists a crossover-like change of the electronic state above room temperature. Temperature dependence of other transport properties studied at high temperatures is also discussed in relation to this anomalous behavior of R H . These results elucidate the formation process of the abnormal metallic state of high- T c oxides at low temperatures, the existence of which characterizes the metal-insulator transition of the Cu-oxide system as a new-type Mott-Hubbard transition.

150 citations