A TENTATIVE MODEL FOR HIGH Tc Y-Ba-Cu-O SUPERCONDUCTORS FROM HREM STUDIES

A high Tc Y-Ba-Cu-O superconductor was prepared with a zero-resistance temperature at 89.9K. High resolution electron microscopy (HREM) indicates that the structure of this material is multiphase and looks like some insulating islands surrounded by regions of conductive phase. There exist many defects in the conductive phase which will be transformed into non-crystalline state after prolonged electron bombardment.