Improvement of MTG Process for Preparation and its property of YBCO Superconductor

Dea-Wha Soh

doi:10.18321/ectj345

Abstract

To improve the superconductivity of high temperature YBCO superconductor, it was prepared and examined by MTG (melt-textured growth) process with use of SmBaCuO seed crystal for orientation, additives of Ag and 211 phase for current density and flux pinning, and heat treatment for oxygen absorption. SmBaCuO single crystals were prepared by MTG process with oxygen absorption and analyzed by XRD and Laue technique. It was estimated that optimum value of Y2BaCuO5 (211 phase) contents in the textured YBCO superconductor as flux pinning center was about 20 wt.%. Ag contents have no influence on the critical temperature but have large influence on the critical current density of the textured YBCO. In the YBCO matrix in experiment, 10 wt.% of Y2BaCuO5 was added, the final 211 content of YBCO made by MTG process could reach about 20 wt.% which was the optimum value for the critical current density. The Ag contents in textured YBCO and the effects of Ag on the superconductivity were also examined. A 5x5x2 mm3 single crystal of SmBaCuO grown by the melted-condensed process was used to be the seed crystal in the preparation of YBCO. It was proved that the orientation of YBCO was the same as the orientation of the SmBaCuO seed. The effect of oxygen absorption of the bulk oriented YBCO was studied and the heat treatment of oxygen absorption would be in flowing oxygen, at 400 for about 24 hours. The critical current density of the textured YBCO prepared by the optimum technical conditions was about 7x104 A/cm2 (77K, 0.01T).

Highlights

In recent years, it was investigated on the improvement of critical current density for the high temperature superconductors of YBCO, SmBCO and YbBCO, respectively in the Lab. and presented in the conventional journal, but it would be discussed for the improvement of MTG process limited only for the YBCO superconductor.There are some extra non-superconducting 211 phase of Y2BaCuO5 in the melt-condensed process due to the loss of the liquid phase (BaCuO2+CuO), which was caused by the slow cooling rate in MTG process
In order to improve the superconductivity of large bulk YBCO superconductor, it should be useful taking a seed in YBCO
To improve the superconductivity of the high Tc superconductor, YBaCuO superconductor was prepared by MTG process with use of SmBaCuO seed crystal and additives of Ag, Y2BaCuO5 (211 phase) to eliminate the weak links of the grain boundaries and micro-cracks, to increase the flux pinning effect in the bulk YBCO

Summary

Introduction

It was investigated on the improvement of critical current density for the high temperature superconductors of YBCO, SmBCO and YbBCO, respectively in the Lab. and presented in the conventional journal, but it would be discussed for the improvement of MTG process limited only for the YBCO superconductor.There are some extra non-superconducting 211 phase of Y2BaCuO5 in the melt-condensed process due to the loss of the liquid phase (BaCuO2+CuO), which was caused by the slow cooling rate in MTG process. In the YBCO matrix in experiment, 10wt.% of Y2BaCuO5 was added, the final 211 content of YBCO made by MTG process could reach about 20wt.% which was the optimum value for the critical current density.

Results

Conclusion