Synthesis of c-axis-oriented Sm123 superconductors and their performance as superconducting permanent magnets

The addition of Ag2O up to 20 wt.% could reinforce its mechanical strength and led us to grow the c-axis-oriented single-domain Sm123 superconductors up to a diameter of 36 mm. The trapped field at 77 K reached 2.1 T and increased to 9 T at 25 K. The maximum trapped field is found to be limited by fracture due to the magnetic stress, which causes the crack to initiate from the region under the seed crystal near the center of the sample with its subsequent propagation through voids. The amount of voids can be substantially reduced when the oxygen partial pressure is increased at the early stage of the melt-processing. The Ba/Sm substitution effect degrades the superconducting performance and lowers the superconducting transition temperature to 80 K only near the central region. The trapped field after drilling a hole through the center of the sample was measured. Its potential use is suggested in practical application. (C) 2000 Elsevier Science B.V. All rights reserved.