  Silver (Ag) is an established additive for improving the mechanical
properties of single grain, (RE)BCO bulk superconductors (where RE = Sm, Gd and
Y). The presence of Ag in the (RE)BCO bulk composition, however, typically
reduces the melting temperature of the single crystal seed in the top seeded
melt growth (TSMG) process, which complicates significantly the controlled
nucleation and subsequent epitaxial growth of a single grain, which is
essential for high field engineering applications. The reduced reliability of
the seeding process in the presence of Ag is particularly acute for the SmBCO
system, since the melting temperature of SmBCO is very close to that of the
generic NdBCO(MgO) seed. SmBCO has the highest superconducting transition
temperature, Tc, and exhibits the most pronounced "peak" effect at higher
magnetic field of all materials in the family of (RE)BCO bulk superconductors
and, therefore, has the greatest potential for use in practical applications
(compared to GdBCO and YBCO, in particular). Development of an effective
seeding process, therefore, is one of the major challenges of the TSMG process
for the growth of large, high quantity single grain superconductors. In this
paper, we report a novel technique that involves introducing a buffer layer
between the seed crystal and the precursor pellet, primarily to inhibit the
diffusion of Ag from the green body to the seed during melt processing in order
to prevent the melting of the seed. The success rate of the seeding process
using this technique is 100% for relatively small batch samples. The
superconducting properties, Tc, Jc and trapped fields, of the single grains
fabricated using the buffers are reported and the micro-structures in the
vicinity of the buffer of single grains fabricated by the modified technique
are analysed.
