Suppression of samarium diffusion in top seeded melt growth processed Y123 superconductors using a Sm123 seed

To suppress the samarium diffusion from a SmBa2Cu3O7−y (Sm123) seed into an YBa2Cu3O7−y (Y123) compact during a top seeded melt growth (TSMG) process, Y211 buffer disks of various thicknesses (t) were inserted at the seed/compact interface. The effectiveness of the Y211 buffer insert on the suppression of samarium diffusion was estimated from the susceptibility curve and composition analysis for the three top surface regions (region just below the seed/buffer, intermediate region between the buffer and compact edge and compact edge). The difference in the superconducting temperature (Tc) and the superconducting transition width (ΔT) in the three regions was large, when no buffer or thin buffers (t is smaller than 1 mm) were used. As a buffer disk of an appropriate thickness was inserted into the seed/compact interface, the difference in Tc and ΔT in the three regions was much reduced. The composition analysis across the seed/buffer/compact region clearly revealed that the Tc decrease was caused by the samarium diffusion from a seed, which led to the formation of Y1−xSmxBa2Cu3O7−y in the Y123 compact region. The buffer insert technique was demonstrated to insure the uniform superconducting properties of the top surface of TSMG processed Y123 superconductors.

► We study effects of buffers on surface properties of Y123 superconductors.
► We examine a superconducting transition temperature and current density.
► Samarium diffusion from a seed decreases the surface properties.
► Buffer blocks are very effective in suppressing the samarium diffusion from a seed.
► Uniform surface properties can be obtained by using of buffers.