Trapped magnetic field of 48 mm diameter single-domain Dy-123 system superconductor

Abstract

Since melt-textured rare earth (RE)-system superconducting bulk can trap high magnetic field, it acts as a quasi-permanent magnet stronger than conventional permanent magnets. Large-sized single-domain DyBa2Cu3Ox (Dy-123) system bulks about 48 mm in diameter and 15 mm in thickness were prepared with a seeding and temperature gradient method in air. Dy-123 and Dy2BaCuO5 (Dy-211) powders were mixed in molar ratios of 1:0.3. The pellets were partially melted at 1,070°C. When the top temperature of the sample reached 980°C, Nd-123 seed crystal was placed on the top surface of the bulk. Then, the samples were cooled from 980°C to 930°C, and then with furnace cooling. Finally, the samples were annealed in pure oxygen atmosphere. When magnetic field of 1.5 T was applied to the samples, the maximum trapped magnetic field of 0.7 T was trapped at 77.3 K in the samples prepared with the cooling time for 600 hr and 700 hr from 980°C to 930°C. Only 0.2 T was trapped in the sample prepared with the cooling time for 1,000 hr, whose bottom part was decomposed due to long time heating.