STUDY OF THE EFFECT OF Ag DOPING IN Y.Ea-Cu-O SUPERCONDUCTING FILMS

Abstract

I prepared the Ag doped YBa2Cu307_o (Ag-YBCO) bulk pellets of undoped, 3 wt%, 7wt%, and 10 wt% and grew films on a P-type (100) oriented single side polished Si-substrate by "screen printing method" using isopropyl alcohol as a binder. The crystal structure is characterized by X-ray diffraction analysis (XRD). The X-ray diffraction analysis revealed that, the pellets annealed in oxygen atmosphere [at the flow rate of 3.5 Kg/cm2] preserved the YBCO phase. The effect of Ag addition on the microstructure is investigated by scanning electron microscopy (SEM). A comparison between YBCO and YBCO+Ag2O pellets revealed considerable difference in surface morphology. The grain size of YBCO increases from 8.05 ,um to 12.25 ,um as doping increases from 0 wt% to 7 wt%, which showed a correlation with improved microstructure, while YBCO particle grain size is almost independent of Ag doping in YBCO films grown on Si-substrate, due to chemical reactivity between YBa2Cu307_ s and Si-substrate. The improvement in superconducting properties of Ag doped YBCO pellets has been interpreted using a two-dimensional growth model. Experimental evidence in support of growth model is presented by carrying out EPMA analysis of 10 wt% Ag doped sample, the corresponding spectrum show that no silver is found inside the grain and accumulated only where grain boundaries connected. The SEMmicrograph of YBCO film grown by screen printing method show that, films have higher void density, while SEM micrograph for 3 wt% Ag doped film at lower magnification have smaller voids than the undoped film.