STUDY OF THE SYNTHESIS PROCESS AND STRUCTURAL DEFECTS IN Y-123 SUPERCONDUCTING SYSTEMS BY POSITRON EXPERIMENT

Using positron annihilation,X-ray diffraction and scanning electron microscopy experiments,the structural characteristics and preparation techniques for YBa2Cu3O7-δ systems are systematically studied.The results show that,for the samples sintered at 950℃,the orthorhombic disorder increases with the duration of sintering time.On the whole,with the increase of sintering temperature and time,the positron lifetime increases until it reaches a saturation value.It is proved that,under the condition of 920—950℃ for 12—72 h,the structural characteristics and superconductivity of Y-123 have good stability.The changes of defect with the sintering temperature and time are also discussed.This experimental results indicate that the positron experiment shows good stability and reliability.