The effect of the grain alignment on the levitation force in single domainYBa2Cu3Oy bulk super-conductors

Single-domain YBa2Cu3Oy. (YBCO) bulk superconductors (Phi 30 x 15 mm(3)) wi th high levitation force of 70 N have been fabricated by modified melt-text ured growth process. The sample was cut into a group of small rectangular s amples with the same dimension of 3.5 x 3.5 x 5 mm3 along different grain-o rientation, The levitation force of the small samples has been measured at liquid nitrogen temperature. It is found that the levitation force decrease s monotonously from theta = 0 degrees to 90 degrees, where theta is the ang le between the c-axis and the normal to the polished surfaces. A simple mod el has been proposed to interpret the experimental result, which is in good agreement with the experimental data. (C) 1999 Elsevier Science B.V. All r ights reserved.