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摘要
The calcination temperature was studied for optimum processing conditions for preparing (Nd0.33Eu0.33Gd0.33) Ba2Cu3O (y) (NEG-123) and (Nd0.33Eu0.33Gd0.33)(2)BaCuO5 (NEG-211) powders with good quality and fine size. This study used commercially available raw powders of Nd2O3, Eu2O3, Gd2O3, BaO2, and CuO in a purity of 99.9 % with 3-5- mu m particle size. These raw powders were carefully weighed to have the compositions of NEG-123 and NEG-211 and pressed into pellets 25 g in weight. The samples were placed in a box furnace under ambient atmosphere and heated to temperatures of 820, 840, 860, and 880 C-a similar to at a rate of 100 C-a similar to/h, held there for 24 h, followed by cooling at 100 C-a similar to/h. X-ray diffraction analyses showed that almost all the samples are single phase except NEG-123 processed at 820 C-a similar to. The average particle size of NEG-123 powders increased with increasing processing temperatures, while that of NEG-211 remained in the same range below 5 mu m irrespective of the treatment temperature. Since the particle size of NEG-123 powders was around 10 mm, one need to refine the particle size below 5 mu m with a technique like mechanical grinding for the production of high J (c) NEG-Ba-Cu-O bulk super conductors. NEG-211 powders will be suitable for such a use in the present form. The homemade powders were used to fabricate NEG-Ba-Cu-O bulk by cold top seeding melt growth with MgO seed following by oxygen annealing treatment. The characterization of bulk demonstrated critical temperature at 65 K with maximum critical current density of 70,000 kA/cm (2) at 10 K with H//c-axis.
- 出版日期2016-5
