EFFECT OF THERMAL TREATMENTS ON THE SUPERCONDUCTIVITY OF UNDOPED AND WO3 DOPED Y-BA-CU-O SYSTEM

Undoped and WO3-doped Y-Ba-Cu-O ceramics have been slowly cooled in fl owing oxygen or quenched in air from 900 degrees C to room temperature , after sintering at 900 degrees C for 30h in flowing oxygen. The ac s usceptibility measurements show that the T-c of the quenched WO3-doped Y-Ba-Cu-O superconductor can reach 88K, while the undoped Y-Ba-Cu-O c eramic quenched in air is a non-superconductor. X-ray diffraction data show that WO3 does nor enter into the YBa2Cu3O7-x lattice but forms a n impurity phase. The WO3-doped YBCO specimens quenched in air consist of orthorhombic YBa2Cu3O7-x phase and an impurity phase which increas es with increasing WO3 content. Raman spectra show that oxygen content s are different for undoped and WO3-doped samples. It is suggested tha t suitable doping with WO3 can change the oxygen content and reduce th e effect of thermal treatments on the superconductivity of Y-Ba-Cu-O s ystem.