The growth of crystals of the high T c oxide superconductors has been hampe red by the complexities of the materials and their phase diagrams.The most common crys tal growth technique adopted for these oxides is the ...The growth of crystals of the high T c oxide superconductors has been hampe red by the complexities of the materials and their phase diagrams.The most common crys tal growth technique adopted for these oxides is the “flux”method,where the st arting materials are solved in a melt,which is usually formed by excess CuO and BaO or a KCl/NaCl mixture.The crystals are produced by slow cooling of the heate d solvent.This method,however,suffers from several disadvantages: (1) the crystals are contaminated with the crucible material, (2) the crystals are difficult to remove from the crucible, (3) the crystals contain flux inclusions.展开更多
The Raman and infrared spectra, resistivity as well as thermoelectric power of Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ ( x =0, 0.1, 0.2, 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure character...The Raman and infrared spectra, resistivity as well as thermoelectric power of Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ ( x =0, 0.1, 0.2, 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr 2Cu 2.7 Mo 0.3 O 7- δ cuprates are different from those of RBa 2Cu 3O 7- δ . The variations of the microstructure in Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ with Nd doping affect the carrier distribution, so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC.展开更多
Since Bi2Sr2Ca1Cu2O8＋x（Bi2212） wires are subject to mechanical loadings, degradation of critical current will occur. The effect of compressive loadings on the critical current of Bi2212 wire is studied by consideri...Since Bi2Sr2Ca1Cu2O8＋x（Bi2212） wires are subject to mechanical loadings, degradation of critical current will occur. The effect of compressive loadings on the critical current of Bi2212 wire is studied by considering micro-buckling of filament. A Bi2212 wire is regarded as a unidirectional filament-reinforced composite in the theoretical analysis. By considering the influence of inclusion, the micro-buckling wavelength can be derived by using a two-dimensional model. Based on the experimental results, the critical current is fitted as a function of buckling wavelength. It is found that the decrease of the critical current is directly proportional to the reciprocal of square of the buckling wavelength. Change of micro-buckling wavelength with material parameters is discussed. A critical strain in the wire with a filament bridge is analyzed using the finite element method.展开更多
文摘The growth of crystals of the high T c oxide superconductors has been hampe red by the complexities of the materials and their phase diagrams.The most common crys tal growth technique adopted for these oxides is the “flux”method,where the st arting materials are solved in a melt,which is usually formed by excess CuO and BaO or a KCl/NaCl mixture.The crystals are produced by slow cooling of the heate d solvent.This method,however,suffers from several disadvantages: (1) the crystals are contaminated with the crucible material, (2) the crystals are difficult to remove from the crucible, (3) the crystals contain flux inclusions.
文摘The Raman and infrared spectra, resistivity as well as thermoelectric power of Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ ( x =0, 0.1, 0.2, 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr 2Cu 2.7 Mo 0.3 O 7- δ cuprates are different from those of RBa 2Cu 3O 7- δ . The variations of the microstructure in Y 1- x Nd x Sr 2Cu 2.7 Mo 0.3 O 7- δ with Nd doping affect the carrier distribution, so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC.
基金Project supported by the National Natural Science Foundation of China(Nos.11327802,11472120,and 11421062)the National Key Project of Magneto-Constrained Fusion Energy Development Program(No.2013GB110002)the Fundamental Research Funds for the Central Universities(No.lzujbky-2017-k18)
文摘Since Bi2Sr2Ca1Cu2O8＋x（Bi2212） wires are subject to mechanical loadings, degradation of critical current will occur. The effect of compressive loadings on the critical current of Bi2212 wire is studied by considering micro-buckling of filament. A Bi2212 wire is regarded as a unidirectional filament-reinforced composite in the theoretical analysis. By considering the influence of inclusion, the micro-buckling wavelength can be derived by using a two-dimensional model. Based on the experimental results, the critical current is fitted as a function of buckling wavelength. It is found that the decrease of the critical current is directly proportional to the reciprocal of square of the buckling wavelength. Change of micro-buckling wavelength with material parameters is discussed. A critical strain in the wire with a filament bridge is analyzed using the finite element method.
