분말 반응법에 의한 YBa2Cu3O7-y합성과 벌크 초전도체의 제조

Abstract

(Y123) powders for the fabrication of bulk superconductors were synthesized by the powder reaction method using (99.9% purity), (99.75%) and CuO (99.9%) powders. The raw powders were weighed to the cation ratio of Y:Ba:Cu=1:2:3, mixed and calcined at in air with intermediate repeated crushing steps. It was found that the formation of Y123 powder was more sensitive to reaction temperature than reaction time. The calcined Y123 powder and a mixture of (Y123 + 0.25 mole + 1 wt.% , (Y1.5)) were used as raw powders for the fabrication of poly-grain or single grain superconductors. The superconducting transition temperature () of the sintered Y123 sample was 91 K and the transition width was as large as 11 K, whereas the of the melt-grown Y1.5 sample was 90.5 K and the transition width was 3.5 K. The critical current density () at 77 K and 0 T of the sintered Y123 was 700 , whereas the of the top-seeded melt growth (TSMG) processed Y1.5 sample was . The magnetic flux density (H) at 77 K of the TSMG-processed Y123 and Y1.5 sample showed the 0.53 kG and 2.45 kG, respectively, which are 15% and 71% of the applied magnetic field of 3.5 kG. The high H value of the TSMG-processed Y1.5 sample is attributed to the formation of the larger superconducting grain with fine Y211 dispersion.