Jc and Composition Distribution of YBCO Coated Conductors Fabricated by the TFA-MOD Process

The Trifluoroacetate-Metal Organic Deposition (TFA-MOD) process is one of the most promising fabrication processes for low-cost superconducting coated conductors (CCs) because of its high yield and non-vacuum system. However, in the doping and multi-coating process for the enhancement of critical current (
I
_c
), degradation of
I
_c
often occurs. In this study, to clarify the origin of
I
_c
degradation, we have investigated the local critical current density (
J
_c
) distribution, in-field
J
_c
properties and the variation of composition for TFA-MOD processed YBa
₂
Cu
₃
O
_y
(YBCO) CCs. The local
J
_c
distributions were measured by Scanning Hall-Probe Microscopy for confirming the location of the high/low-
J
_c
regions. The CCs were then cut into 3 mm×3 mm or 3 mm×4 mm for dc magnetization measurement. The
T
_c
of the all samples were about 87 K to 90 K. In-field
J
_c
at 77 K was obtained from
M
-
H
measurements and all the samples were compared with each other. The in-field
J
_c
of high-
J
_c
sample showed about 100 times higher value than that of the low-
J
_c
sample. Then we have observed the microchemistry and the variation of composition by SEM-EDS. In the high-
J
_c
sample, the grains of the superconducting phase were large in size and were connected to each other. This means that superconducting current could form through the whole sample area and generate a large magnetic moment. On the other hand, in the low-
J
_c
sample, though the superconducting phase could be observed, the grains were small in size and sparse. Therefore, the magnetic moment measured was small. However, it was also suggested that the intra-grain
J
_c
would be almost the same as that of high-
J
_c
sample.