The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperat...The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.展开更多
Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film...Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film was irradiated by a 308 nm laser pulse of 25 ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for MgB2 film under ultraviolet laser and then the built-ln electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.展开更多
Pure MgB2 bulk samples are successfully synthesized by self-propagatlng hlgh-temperature synthesis （SHS） method. The experiments show that the best preheating temperature is 250℃, the highest Jc values of the prepa...Pure MgB2 bulk samples are successfully synthesized by self-propagatlng hlgh-temperature synthesis （SHS） method. The experiments show that the best preheating temperature is 250℃, the highest Jc values of the prepared MgB2 reach 1.5×10^6A/cm^2 （10K, 0.5T） and 1.7×10^6A/cm^2 （20K, 0T）, and the MgB2 particle sizes range from 2 to 5μm. The advantages of this method are that it is simple, economical and suitable for the manufacture of bulk MgB2 materials on industrial scale.展开更多
Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The ...Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes.展开更多
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.11174214 and No.11204192）, the Research Project of Education Department in Sichuan Province （No.13ZB0207）, and Scientific Research Project of Yibin University （No.2013YY05）.
基金中国科学院资助项目，Scientific Research Foundation for Returned Overseas Chinese Scholars，Ministry of Education of China
文摘The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.
文摘Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film was irradiated by a 308 nm laser pulse of 25 ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for MgB2 film under ultraviolet laser and then the built-ln electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.
基金Project supported by the Natural Science Foundation of Gansu province of China （Grant No ZS032-B25-019）.
文摘Pure MgB2 bulk samples are successfully synthesized by self-propagatlng hlgh-temperature synthesis （SHS） method. The experiments show that the best preheating temperature is 250℃, the highest Jc values of the prepared MgB2 reach 1.5×10^6A/cm^2 （10K, 0.5T） and 1.7×10^6A/cm^2 （20K, 0T）, and the MgB2 particle sizes range from 2 to 5μm. The advantages of this method are that it is simple, economical and suitable for the manufacture of bulk MgB2 materials on industrial scale.
基金Project supported by the National Natural Science Foundation of China （Grant No 10174006）.
文摘Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes.
