The reactions of stoichiometric Y2O3, CuO, and different Ba salts or oxides (BaCO3, Ba(NO3)(2), BaO2, BaCuO2) for forming various compounds in the Y-Ba-Cu-O system (i.e., YBa2Cu3O7-delta, BaCuO2, Y2BaCuO5 and Y2Cu2O5)...The reactions of stoichiometric Y2O3, CuO, and different Ba salts or oxides (BaCO3, Ba(NO3)(2), BaO2, BaCuO2) for forming various compounds in the Y-Ba-Cu-O system (i.e., YBa2Cu3O7-delta, BaCuO2, Y2BaCuO5 and Y2Cu2O5) were systematically investigated by thermal analysis and X-ray diffractometry. The relevant activation energies were calculated from thermogravimetric data. It is found that the reaction pathway significantly depends on the thermal stability of the Ba precursors. Binary BaO-CuO phases form at low temperature (650 similar to 700 degreesC) when in presence of easy- to -decompose Ba precursors, and then slowly transform to ternary compounds. On the contrary, when Ba ions are released at temperature higher than 900 degreesC, ternary phases form directly from the components.展开更多
Superconducting thin films of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>（Y-Ba-Cu-O） with Tc more than 85K have been deposited in situ by metalorganic chemical vapor deposition ...Superconducting thin films of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>（Y-Ba-Cu-O） with Tc more than 85K have been deposited in situ by metalorganic chemical vapor deposition （MOCVD） on yttria stabilized zirconia（YSZ） substrates. The relationship of film orientation on substrate temperature and the lowest formation temperature region of superconducting phase have been obtained after changing the substrate temperature. The epitaxial relation between Y-Ba-Cu-O films and the YSZ su bstrates were discussed.展开更多
Y-Ba-Cu-O is a promising high temperature superconductor material because of its good electrical and magnetic properties. However, large and complex bulks cannot be made directly, and joining is a good way to solve th...Y-Ba-Cu-O is a promising high temperature superconductor material because of its good electrical and magnetic properties. However, large and complex bulks cannot be made directly, and joining is a good way to solve this problem. Joining Y-Ba-Cu-O with filler material was widely used and reported, but sliced melt solder was rarely reported, especially the one that required relatively short time. In this paper, sliced melt Ag doped Y-Ba-Cu-O was used as filler material and the joining time is relatively shorter compared with mast of the published paper. The melt solder was fabricated and tested, the melting temperature is 975℃and there is much less pores found in the solder compared with the sintered solder. The bonding result is very encouraging： the superconductivity recovery ratio is 97.3%, which is about 5% higher than as sintered filler material. The microstructure in the bonding zone is very similar to that in the base material, no Y2BaCuO5 （ Y211 ） phase accumulated during the joining process, which reveals that high quality superconductive bonding was achieved.展开更多
文摘The reactions of stoichiometric Y2O3, CuO, and different Ba salts or oxides (BaCO3, Ba(NO3)(2), BaO2, BaCuO2) for forming various compounds in the Y-Ba-Cu-O system (i.e., YBa2Cu3O7-delta, BaCuO2, Y2BaCuO5 and Y2Cu2O5) were systematically investigated by thermal analysis and X-ray diffractometry. The relevant activation energies were calculated from thermogravimetric data. It is found that the reaction pathway significantly depends on the thermal stability of the Ba precursors. Binary BaO-CuO phases form at low temperature (650 similar to 700 degreesC) when in presence of easy- to -decompose Ba precursors, and then slowly transform to ternary compounds. On the contrary, when Ba ions are released at temperature higher than 900 degreesC, ternary phases form directly from the components.
文摘Superconducting thin films of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>（Y-Ba-Cu-O） with Tc more than 85K have been deposited in situ by metalorganic chemical vapor deposition （MOCVD） on yttria stabilized zirconia（YSZ） substrates. The relationship of film orientation on substrate temperature and the lowest formation temperature region of superconducting phase have been obtained after changing the substrate temperature. The epitaxial relation between Y-Ba-Cu-O films and the YSZ su bstrates were discussed.
基金Acknowledgements This research is supported by the National Natural Science Foundation of China （ Grant No. 50705050 ） and Beijing Natural Science Foundation （ Grant No. 3093020）.
文摘Y-Ba-Cu-O is a promising high temperature superconductor material because of its good electrical and magnetic properties. However, large and complex bulks cannot be made directly, and joining is a good way to solve this problem. Joining Y-Ba-Cu-O with filler material was widely used and reported, but sliced melt solder was rarely reported, especially the one that required relatively short time. In this paper, sliced melt Ag doped Y-Ba-Cu-O was used as filler material and the joining time is relatively shorter compared with mast of the published paper. The melt solder was fabricated and tested, the melting temperature is 975℃and there is much less pores found in the solder compared with the sintered solder. The bonding result is very encouraging： the superconductivity recovery ratio is 97.3%, which is about 5% higher than as sintered filler material. The microstructure in the bonding zone is very similar to that in the base material, no Y2BaCuO5 （ Y211 ） phase accumulated during the joining process, which reveals that high quality superconductive bonding was achieved.
