The sound velocities of longitudinal and shear waves are measured on a polycrystalline MgB_(2) superconductor with Tc of 39 K. The specimen used in the experiments is pressed and heated using the MgB_(2) powder. The e...The sound velocities of longitudinal and shear waves are measured on a polycrystalline MgB_(2) superconductor with Tc of 39 K. The specimen used in the experiments is pressed and heated using the MgB_(2) powder. The elastic moduli, Debye temperature and specific heat at room temperature are obtained based on sound velocity data. The results indicate that the velocities are much higher than those in the usual materials, while elastic constants remain reasonably soft, which may be due to the high transition temperature of the MgB2 superconductor.展开更多
In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation...In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.展开更多
基金Supported by the Outstanding Youth Fund of the National Natural Science Foundation of China under Grant No.59725105the“Hundreds of Talents”Programme of the Chinese Academy of Sciences。
文摘The sound velocities of longitudinal and shear waves are measured on a polycrystalline MgB_(2) superconductor with Tc of 39 K. The specimen used in the experiments is pressed and heated using the MgB_(2) powder. The elastic moduli, Debye temperature and specific heat at room temperature are obtained based on sound velocity data. The results indicate that the velocities are much higher than those in the usual materials, while elastic constants remain reasonably soft, which may be due to the high transition temperature of the MgB2 superconductor.
基金This work was supported by the "Outstanding Youth Fund" of the National Natural Science Foundation of China (Grant No. 59725105) the "Hundreds of Talents" Program of the Chinese Academy of Sciences.
文摘In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.
