The radiation damage induced by the reactor neutrons in body-centered-cubic metal Nb is simulated by the 81 MeV carbon irradiation to a total dose of 2.5×10^(16)/cm^(2).The created radiation damage and its therma...The radiation damage induced by the reactor neutrons in body-centered-cubic metal Nb is simulated by the 81 MeV carbon irradiation to a total dose of 2.5×10^(16)/cm^(2).The created radiation damage and its thermal annealing behavior are studied by positron annihilation and perturbed angular correlation techniques.The results show the existence of both mono-and di-vacancies in Nb after the irradiation.Most of the defects caused by the radiation damage disappear after annealing around 960K.The radiation damage is completely annealed at 1058K.展开更多
The temperature dependences of the positron annihilation lifetime and the Doppler broadening shape parameters have been measured in high Tc superconductors YBa_(2)Cu_(3)O_(7-x)=between 77.2 and 300K.The measured param...The temperature dependences of the positron annihilation lifetime and the Doppler broadening shape parameters have been measured in high Tc superconductors YBa_(2)Cu_(3)O_(7-x)=between 77.2 and 300K.The measured parameters show an abrupt change across the range of superconducting transition temperature,indicating a change of the electronic structure.The structural instabilities have also been observed in three higher temperature ranges of115-135,150-210 and 250-280K.This suggests that higher Tc superconductors might be found in these temperature ranges.展开更多
Characteristics of superconducting and semiconductor materials with the same composition have been studied at room temperature,94K,and 77K by the positron annihilation technique.The results indicate that the phase tra...Characteristics of superconducting and semiconductor materials with the same composition have been studied at room temperature,94K,and 77K by the positron annihilation technique.The results indicate that the phase transition of electronic strueture in the superconducting material takes place in the superconducting state.展开更多
文摘The radiation damage induced by the reactor neutrons in body-centered-cubic metal Nb is simulated by the 81 MeV carbon irradiation to a total dose of 2.5×10^(16)/cm^(2).The created radiation damage and its thermal annealing behavior are studied by positron annihilation and perturbed angular correlation techniques.The results show the existence of both mono-and di-vacancies in Nb after the irradiation.Most of the defects caused by the radiation damage disappear after annealing around 960K.The radiation damage is completely annealed at 1058K.
基金Project supported partly by International Atomic Energy Agency under contract number 5295/RB.
文摘The temperature dependences of the positron annihilation lifetime and the Doppler broadening shape parameters have been measured in high Tc superconductors YBa_(2)Cu_(3)O_(7-x)=between 77.2 and 300K.The measured parameters show an abrupt change across the range of superconducting transition temperature,indicating a change of the electronic structure.The structural instabilities have also been observed in three higher temperature ranges of115-135,150-210 and 250-280K.This suggests that higher Tc superconductors might be found in these temperature ranges.
文摘Characteristics of superconducting and semiconductor materials with the same composition have been studied at room temperature,94K,and 77K by the positron annihilation technique.The results indicate that the phase transition of electronic strueture in the superconducting material takes place in the superconducting state.
