The addition Of Pb enhances the hightemperature stability as well as theproportion of the high Tphase in Bi-Sr-Ca-Cu-O superconductor.The sample A with nominal composi-tion of BiSrCaCuOwas synthesized bySolid state re...The addition Of Pb enhances the hightemperature stability as well as theproportion of the high Tphase in Bi-Sr-Ca-Cu-O superconductor.The sample A with nominal composi-tion of BiSrCaCuOwas synthesized bySolid state reaction.It was sintered in airat 1153K for 24h,followed by annealingat 773K for 24h and furnace-cooling.The sample B with a nominal compositionof BiPbSrCaCuOwas prepared bymixing PbO with the powder ofBiSrCaCuOwhich had been prefired at1113K for 24h,pressing,sintering at展开更多
The present work investigates the effect of europium substitution on the （Bi, Pb）-2212 system in the concentration range 0.5 ≤ x ≤1.0. Phase analysis and lattice parameter calculations on the powder diffraction da...The present work investigates the effect of europium substitution on the （Bi, Pb）-2212 system in the concentration range 0.5 ≤ x ≤1.0. Phase analysis and lattice parameter calculations on the powder diffraction data and the elemental analysis of EDX show that the Eu atoms are successfully substituted into the （Bi, Pb）-2212 system. Resistivity measurements （64-300 K） reveal that the system exhibits superconductivity at x ≤ 0.5 and semiconductivity at x 〉 0.5. With the complete suppression of superconductivity which is known to be a quasi-two dimensional phenomenon in these materials, a metal to insulator transition takes place at x = 0.6 and the predominant conduction mechanism is found to be variable range hopping between localized states, resulting in macroscopic semiconducting behaviour. The results of electrical and structural properties of the doped （Bi, Pb）-2212 compounds suggest that the decrease of charge carrier concentration and the induced structural disorder are the more effective and dominant mechanisms in the origin of the metal to insulator transition and suppression of superconductivity due to Eu substitution at its Sr site.展开更多
Amorphous Bi(Pb)-Sr-Ca-Cu-O strips of types(1112)and(2212)were made by means of non-equilibrium solidification of melt-quenching method,On the surface of glassy strip,the flexible(2212)superconducting whiskers have be...Amorphous Bi(Pb)-Sr-Ca-Cu-O strips of types(1112)and(2212)were made by means of non-equilibrium solidification of melt-quenching method,On the surface of glassy strip,the flexible(2212)superconducting whiskers have been obtained.The growth and feature of superconducting whiskers were studied in detail.展开更多
In this paper, samples of antimony doped Bi-based superconductor with stoichiometric composition Bi1.7Pb0.2Sb0.1Sr2Ca2Ca3O10 were prepared by a solid state reaction method. The effect of sintering time on the supercon...In this paper, samples of antimony doped Bi-based superconductor with stoichiometric composition Bi1.7Pb0.2Sb0.1Sr2Ca2Ca3O10 were prepared by a solid state reaction method. The effect of sintering time on the superconducting properties was studied;all samples were sintered in air at 850°C for different sintering time (80, 100, 120, 140, and 160) h. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed for determination of the crystal structure and surface morphology of samples, respectively. All samples showed an orthorhombic structure with two phases, high-Tc phase (2223) and low-Tc phase (2212) in addition to an impure phase. It has been observed that the critical temperature and the high-Tc phase increases and appears to be the dominant phase when the sintering time is increased to 140 h, while with increasing sintering time to 160 h, both Tc and the high phase started to decrease. (SEM) results show that increasing sintering time enhances the growing of superconducting phase unidirectional and suppresses the high phase intrusion which leads to the production of nearly single Bi-2223 phase with higher Tc.展开更多
Ⅰ. INTRODUCTION Up to now, the reported superconductor with the highest zero resistance T<sub>c0</sub> being 125 K is Tl-system oxide. But research and application of the system are extremely restrained b...Ⅰ. INTRODUCTION Up to now, the reported superconductor with the highest zero resistance T<sub>c0</sub> being 125 K is Tl-system oxide. But research and application of the system are extremely restrained because of the easy vaporization and terrific poison of Tl<sub>2</sub>O<sub>3</sub>. Apart from the Tl-system, a superconductor, Bi<sub>1.65</sub>Pb<sub>0.35</sub>Sr<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>9.3</sub>F<sub>0.7</sub>, with the highest T<sub>c0</sub> being 118 K and transi-展开更多
I. INTRODUCTIONFrom the reflection-absorption spectra, Raman spectra and fluorescence spectra etc. of Y-Ba-Cu-O high T_c superconductor, much information concerning the structure of energy band, the density of states ...I. INTRODUCTIONFrom the reflection-absorption spectra, Raman spectra and fluorescence spectra etc. of Y-Ba-Cu-O high T_c superconductor, much information concerning the structure of energy band, the density of states and the electron-phonon coupling strength has been obtained. The discovery of Bi-Sr-Ca-Cu-O system indicates a new direction for the re-展开更多
By using TEM, XPS, IR, position annihilation and differential specific heat measurements, the properties and structure of the F-doped (Bi, Pb)-Sr-Ca-Cu-O superconductor have been studied. The results show that the flu...By using TEM, XPS, IR, position annihilation and differential specific heat measurements, the properties and structure of the F-doped (Bi, Pb)-Sr-Ca-Cu-O superconductor have been studied. The results show that the fluorine atoms are homogeneously distributed in superconducting phase and substituted for the oxygen atoms at O(2) crystallographic sites; the Pb-F and Cu-F bonds are formed. F-doping results in the variance of the incommensurate modulation structure, the increase of the point defects and chemical pressure, the enhancement of flux pinning effect and the change of the electronic structure and chemical bond, and greatly improves superconductive properties of the 2223 phase (Bi, Pb)-Sr-Ca-Cu-O.展开更多
文摘The addition Of Pb enhances the hightemperature stability as well as theproportion of the high Tphase in Bi-Sr-Ca-Cu-O superconductor.The sample A with nominal composi-tion of BiSrCaCuOwas synthesized bySolid state reaction.It was sintered in airat 1153K for 24h,followed by annealingat 773K for 24h and furnace-cooling.The sample B with a nominal compositionof BiPbSrCaCuOwas prepared bymixing PbO with the powder ofBiSrCaCuOwhich had been prefired at1113K for 24h,pressing,sintering at
基金supported by Kerala State Council for Science,Technology and Environment,Council of Scientific and Industrial Researchthe University Grants Commission of India
文摘The present work investigates the effect of europium substitution on the （Bi, Pb）-2212 system in the concentration range 0.5 ≤ x ≤1.0. Phase analysis and lattice parameter calculations on the powder diffraction data and the elemental analysis of EDX show that the Eu atoms are successfully substituted into the （Bi, Pb）-2212 system. Resistivity measurements （64-300 K） reveal that the system exhibits superconductivity at x ≤ 0.5 and semiconductivity at x 〉 0.5. With the complete suppression of superconductivity which is known to be a quasi-two dimensional phenomenon in these materials, a metal to insulator transition takes place at x = 0.6 and the predominant conduction mechanism is found to be variable range hopping between localized states, resulting in macroscopic semiconducting behaviour. The results of electrical and structural properties of the doped （Bi, Pb）-2212 compounds suggest that the decrease of charge carrier concentration and the induced structural disorder are the more effective and dominant mechanisms in the origin of the metal to insulator transition and suppression of superconductivity due to Eu substitution at its Sr site.
文摘Amorphous Bi(Pb)-Sr-Ca-Cu-O strips of types(1112)and(2212)were made by means of non-equilibrium solidification of melt-quenching method,On the surface of glassy strip,the flexible(2212)superconducting whiskers have been obtained.The growth and feature of superconducting whiskers were studied in detail.
文摘In this paper, samples of antimony doped Bi-based superconductor with stoichiometric composition Bi1.7Pb0.2Sb0.1Sr2Ca2Ca3O10 were prepared by a solid state reaction method. The effect of sintering time on the superconducting properties was studied;all samples were sintered in air at 850°C for different sintering time (80, 100, 120, 140, and 160) h. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed for determination of the crystal structure and surface morphology of samples, respectively. All samples showed an orthorhombic structure with two phases, high-Tc phase (2223) and low-Tc phase (2212) in addition to an impure phase. It has been observed that the critical temperature and the high-Tc phase increases and appears to be the dominant phase when the sintering time is increased to 140 h, while with increasing sintering time to 160 h, both Tc and the high phase started to decrease. (SEM) results show that increasing sintering time enhances the growing of superconducting phase unidirectional and suppresses the high phase intrusion which leads to the production of nearly single Bi-2223 phase with higher Tc.
基金Project supported by the National Natural Science Foundation of China.
文摘Ⅰ. INTRODUCTION Up to now, the reported superconductor with the highest zero resistance T<sub>c0</sub> being 125 K is Tl-system oxide. But research and application of the system are extremely restrained because of the easy vaporization and terrific poison of Tl<sub>2</sub>O<sub>3</sub>. Apart from the Tl-system, a superconductor, Bi<sub>1.65</sub>Pb<sub>0.35</sub>Sr<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>9.3</sub>F<sub>0.7</sub>, with the highest T<sub>c0</sub> being 118 K and transi-
基金Project supported by the National Natural Science Foundation of China.
文摘I. INTRODUCTIONFrom the reflection-absorption spectra, Raman spectra and fluorescence spectra etc. of Y-Ba-Cu-O high T_c superconductor, much information concerning the structure of energy band, the density of states and the electron-phonon coupling strength has been obtained. The discovery of Bi-Sr-Ca-Cu-O system indicates a new direction for the re-
文摘By using TEM, XPS, IR, position annihilation and differential specific heat measurements, the properties and structure of the F-doped (Bi, Pb)-Sr-Ca-Cu-O superconductor have been studied. The results show that the fluorine atoms are homogeneously distributed in superconducting phase and substituted for the oxygen atoms at O(2) crystallographic sites; the Pb-F and Cu-F bonds are formed. F-doping results in the variance of the incommensurate modulation structure, the increase of the point defects and chemical pressure, the enhancement of flux pinning effect and the change of the electronic structure and chemical bond, and greatly improves superconductive properties of the 2223 phase (Bi, Pb)-Sr-Ca-Cu-O.
