Dj. Miller et al., BRICK-WALL STRUCTURE IN POLYCRYSTALLINE TLBA2CA2CU3OX THICK-FILMS WITH HIGH CRITICAL CURRENTS, Applied physics letters, 63(4), 1993, pp. 556-558
Microstructural studies of TlBa2Ca2Cu3Ox(TI-1223) thick films that exh
ibit high critical current densities (J(c)) for nonepitaxial polycryst
alline materials show that these films possess a ''brick-wall'' struct
ure that may be partly responsible for high current densities. The mag
netic field dependence of J(c) is similar to that reported for Bi-Sr-C
a-Cu-0 materials that exhibit this structure. Structural analyses indi
cate a high degree of c-axis alignment but little in-plane texture, su
ggesting that high-angle [001] tilt boundaries are prevalent. Scanning
and transmission electron microscopy reveal that the microstructure c
onsists of overlapping layers reminiscent of the brick-wall structure.
These results suggest that high critical current densities may be ach
ieved by percolative transport through this structure.