Bulk Superconductivity of Y-Ba-Cu-O and Er-Ba-Cu-O

High T c superconductivity in Y-Ba-Cu-O prepared with the improved conditions are investigated by both elctrical resistivity and magnetic susceptibility measurements. The results provide a clear evidence for the bulk superconductivity in this oxide material. A discovery of new supercoducting oxide Er-Ba-Cu-O with transition temperature as high as 90 K is also reported. It is found that these two compound shows very similar X-ray diffraction patterns and, thus, it is likely that the high T c superconductivity is realized in the common crystal structure.