采用光学浮区法生长了层状过渡金属氧化物Bi2Sr2-x Ca x Co2O y(x=0,2)晶体。通过XRD,SEM和TEM结构表征,表明了生长的晶体为层状晶体,并确定了晶体生长的方向垂直与c轴。研究了晶体的热电性能,包括Bi2Ca2Co2O y和Bi2Sr2Co2O y晶体ab面的...采用光学浮区法生长了层状过渡金属氧化物Bi2Sr2-x Ca x Co2O y(x=0,2)晶体。通过XRD,SEM和TEM结构表征,表明了生长的晶体为层状晶体,并确定了晶体生长的方向垂直与c轴。研究了晶体的热电性能,包括Bi2Ca2Co2O y和Bi2Sr2Co2O y晶体ab面的Seeback系数和电阻率,表明了Bi2Ca2Co2O y具有较好的热电势和电导,并分析了电输运性能与晶体失配结构的关系。展开更多
High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resisti...High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,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
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
Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1-xYxCu2O8＋δ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ...Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1-xYxCu2O8＋δ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ranging from 4.2 K to 295 K are measured. A pulse technique is used to reduce sample heating for the measurement near pseudogap opening temperature T^＊ - 280 K. Our experimental results show that the superconducting gap, the peakdip separation, and the pseudogap opening temperature are all increased as compared with those from near optimally doped samples, which requires further theoretical analysis in the future.展开更多
文摘采用光学浮区法生长了层状过渡金属氧化物Bi2Sr2-x Ca x Co2O y(x=0,2)晶体。通过XRD,SEM和TEM结构表征,表明了生长的晶体为层状晶体,并确定了晶体生长的方向垂直与c轴。研究了晶体的热电性能,包括Bi2Ca2Co2O y和Bi2Sr2Co2O y晶体ab面的Seeback系数和电阻率,表明了Bi2Ca2Co2O y具有较好的热电势和电导,并分析了电输运性能与晶体失配结构的关系。
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 10904030)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091301120002)
文摘High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,
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.
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.
基金Project supported by the National Natural Science Foundation of China(Grant No.10974242)
文摘Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1-xYxCu2O8＋δ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ranging from 4.2 K to 295 K are measured. A pulse technique is used to reduce sample heating for the measurement near pseudogap opening temperature T^＊ - 280 K. Our experimental results show that the superconducting gap, the peakdip separation, and the pseudogap opening temperature are all increased as compared with those from near optimally doped samples, which requires further theoretical analysis in the future.
