CD shopping page |
2011-Sustainable Industrial Processing Summit
|
| Editors: | Florian K |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2012 |
| Pages: | 646 pages |
| ISBN: | 978-0-9879917-6-8 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Influence of both cooling rate and TeO2 addition on the properties of YBCO superconductor
Yasser Ahmed1;1CENTRAL METALLURGICAL RESEARCH AND DEVELOPMENT INS, Cairo, Egypt;
Type of Paper: Regular
Id Paper: 558
Topic: 9
Abstract:
Samples of the composite superconducting system YBCO- TeO2 were prepared using solid state reaction technique. Different weight percentages of TeO2 were added to the main mixture component for YBCO formation. The weight percentages of TeO2 is ranged from 0.0 to 4 wt% for finally prepare the composite system [YBa2Cu3O7-y]1-x(TeO2)x. The samples were cooled down from 940 oC to room temperature by two different cooling procedures: 1- slow cooling (1- 2 oC/min), and 2- direct quenching in oxygen gas in about 45 seconds. XRD analysis and temperature-resistivity measurements showed that the addition of TeO2 caused a rapid phase transformation from tetragonal to orthorhombic in a very short time upon quenching to room temperature. All quenched samples showed a phase difference between the sample outer surface (Orthorhombic) and its interior (Tetragonal). On the other hand, the slowly cooled samples did not show such a phase difference. It is mainly composed of one single orthorhombic phase. Doping the material YBCO with TeO2 led to the formation of secondary phases that co-exist with the 123 parent phase without affecting its crystal structure. Those inter-granular secondary phases led to a semi-conducting behavior in normal state and caused a gradual decrease in the samples Tc- values with increasing Te-content. It also increased the bulk densities of the samples and reduced their degree of degradation in moisture environment.