• 한국결정성장학회지
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• 제21권5호
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• pp.199-204
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• 2011

존멜팅법을 이용해서 $(YSmNd)_{1.8}Ba_{2.4}Cu_{3.4}O_{7-x}$계 고온초전도체를 대기 중에서 용융성장실험을 하였다. 존멜팅법의 최적용융온도는 $1100^{\circ}C$였으며 성장속도는 3.5 mm/h 였다. 한 방향으로 용융성장 된 (YSN)1.8 초전도체는 XRD, 광학현미경, TEM을 이용하여 미세구조를 관찰하였으며 SQUID magnetometer와 직접전류수송법을 이용해 초전도특성을 평가하였다. 특히 용융성장 된 (YSN)1.8 초전도체의 광학현미경에 의한 미세구조 관측 결과 초전도상인 (YSN)123 matrix내에 비초전도상인 (YSN)211 inclusions이 균질하게 분포되어 있는 것이 관측되었다. 또한 용융성장 된 (YSN)1.8 초전도체는 90 K 이상의 임계온도 특성을 보였으며 액체질소 안에서 직접전류수송법으로 측정한 결과 수송전류 830 A에서 $3.93{\times}10^4$(A/$cm^2$)를 갖는 높은 임계전류밀도 특성을 보였다.

• 한국재료학회지
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• 제22권11호
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• pp.569-574
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• 2012

Large single grain $Gd_{1.5}Ba_2Cu_3O_{7-y}$ (Gd1.5) bulk superconductors were fabricated by a top-seeded melt growth (TSMG) process using an $NdBa_2Cu_3O_{7-y}$ seed. The seeded Gd1.5 powder compacts with a diameter of 50 mm were subjected to the heating cycles of a TSMG process. After the TSMG process, the diameter of the single grain Gd1.5 compact was reduced to 43 mm owing to the volume contraction during the heat treatment. The superconducting transition temperature ($T_c$) of the top surface of the single grain Gd1.5 sample was as high as 93.5 K. The critical current densities ($J_cs$) at 77 K and 1T and 1.5 T were in ranges of 25,200-43,900 $A/cm^2$ and 10,000-23,000 $A/cm^2$, respectively. The maximum attractive force at 77 K of the sample field-cooled using an Nd-B-Fe permanent magnet (surface magnetic field of 0. 527 T) was 108.3 N; the maximum repulsive force of the zero field-cooled sample was 262 N. The magnetic flux density of the sample field-cooled at 77 K was 0.311T, which is approximately 85% of the applied magnetic field of 0.375 T. Microstructure investigation showed that many $Gd_2BaCuO_5$ (Gd211) particles of a few ${\mu}m$ in size, which are flux pinning sites of Gd123, were trapped within the $GdBa_2Cu_3O_{7-y}$ (Gd123) grain; unreacted $Ba_3Cu_5O_8$ liquid and Gd211 particles were present near the edge regions of the single grain Gd1.5 bulk compact.