Characterization of the surface of shock-compacted YB2C3Oy particles

The shock compaction effects on the structural and superconducting properties of high-Tc YB2C3Oy particles are investigated. YB2C3Oy particles with an average size of 960 nm were prepared by the dry-type jet mill. The lattice constants of the orthorhombic cell with a ˆ 0:383 nm, b ˆ 0:390 nm and c ˆ 1:17 nm for as-shocked YB2C3Oy particles are calculated just after the shock compaction under 5.71 GPa. In the measurements of susceptibility by SQUID magnetometer, DM is obtained. It is found that DM(0.00232 emu/g) for as-shocked YB2C3Oy particles after annealing at 8708C for 10 h is larger than DM(0.00047 emu/g) for as-shocked YB2C3Oy particles, which seems to indicate the new pinning centres created around the grain boundaries during annealing. From scanning electron microscopy observations, the surface of the specimens for asshocked YB2C3Oy has large grains of 4±15 mm in length partly with large growth-steps caused mainly by heats generated in shock compaction. Also from the section analysis of atomic force microscope image, the vertical distance of about 30±80 nm is obtained around the edge area in annealed YB2C3Oy grains. # 2001 Elsevier Science B.V. All rights reserved