Study of selenium doped Bi-based superconductors by AES and SEM

Compositions in Bi2Sr2Ca2Cu3Oy:Se-x with x = 0, 0.05, 0.1, 0.2, 0.3, 0.4 ha ve been prepared by the solid state reaction method. The samples have initi ally been studied by the X-ray powder diffraction method for structural cha racterization. Superconducting transition temperatures (T) measured by the four probe technique shows dependence on selenium concentration. A detailed microstructural analysis has been carried out by scanning electron and Aug er electron spectroscopies in order to investigate the incorporation of sel enium in the grains of the superconductors. It is found that Se concentrati on affects both the T values and the morphology of the grains. AES studies clearly show the presence of selenium in the grains of the superconductor.