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RRR and thermal conductivity of Ag and Ag-0.2 wt.%Mg alloy in Ag/Bi-2212 wires
| Content Provider | Scilit |
|---|---|
| Author | Li, P. Ye, L. Jiang, J. Shen, T. |
| Copyright Year | 2015 |
| Description | Journal: Iop Conference Series: Materials Science and Engineering Residual resistivity ratio (RRR) and thermal conductivity of metal matrix in metal/superconductor composite wires are important parameters for designing superconducting magnets. However, the resistivity of silver in reacted Ag/Bi-2212 wires has yet to be determined over temperature range from 4.2 K to 80 K because Bi-2212 filaments have a critical transition temperature $T_{c}$ of ~ 80 K, and because it is unknown whether the RRR of Ag/Bi-2212 degrades with Cu diffusing from Bi-2212 filaments into silver sheathes at elevated temperatures and to what degree it varies with heat treatment. We measured the resistivity of stand-alone Ag and AgMg (Ag-0.2 wt.% Mg) wires as well as the resistivity of Ag and Ag-0.2 wt.% Mg in Ag/Bi- 2212 round wires reacted in 1 bar oxygen at 890 °C for 1, 8, 24 and 48 hours and quickly cooled to room temperature. The heat treatment was designed to reduce the critical current $I_{c}$ of Bi- 2212 wires to nearly zero while allowing Cu loss to fully manifest itself. We determined that pure silver exhibits a RRR of ~ 220 while the oxide-dispersion strengthened Ag-Mg exhibits a RRR of ~ 5 in stand-alone samples. A surprising result is that the RRR of silver in the composite round wires doesn't degrade with extended time at 890 °C for up to 48 hours. This surprising result may be explained by our observation that the Cu that diffuses into silver tends to form $Cu_{2}$O precipitates in oxidizing atmosphere, instead of forming Ag-Cu solution alloy. We also measured the thermal conductivity and the magneto-resistivity of pure Ag and Ag-0.2 wt. % Mg from 4.2 K to 300 K in magnetic fields up to 14.8 T and summarized them using a Kohler plot. |
| Related Links | http://iopscience.iop.org/article/10.1088/1757-899X/102/1/012027/pdf |
| ISSN | 17578981 |
| e-ISSN | 1757899X |
| DOI | 10.1088/1757-899x/102/1/012027 |
| Journal | Iop Conference Series: Materials Science and Engineering |
| Issue Number | 1 |
| Volume Number | 102 |
| Language | English |
| Publisher | IOP Publishing |
| Publisher Date | 2015-12-18 |
| Access Restriction | Open |
| Subject Keyword | Journal: Iop Conference Series: Materials Science and Engineering Condensed Matter Physics Thermal Conductivity Ag and Ag |
| Content Type | Text |
| Resource Type | Article |
