Critical Current Properties in $\hbox{REBa}_{2} \hbox{Cu}_{3}\hbox{O}_{y}$ Films With Nanorods Depending on Growth Conditions

Growth temperature (
T
_s
) dependent microstructures of nanorods were clarified for BaNb
₂
O
₆
(BNO)-doped YBa
₂
Cu
₃
O
_y
(Y123) films. The morphology of BNO in the Y123 matrix was changed from fluctuated nanorods to uniform nanorods with the increase in
T
_s
. Reflecting this change in the nanorod morphology, spatial distribution of local critical current density (
J
_cl
) determined from the percolation transition model became sharp with the increase in
T
_s
. The sharp distribution of
J
_cl
led to a steep slope of electric field vs. current density curve and a sharp
J
_c
peak under
B
//
c
in the magnetic field angular dependence. The evaluation of the distribution of
J
_cl
is a strong tool to understand quantitatively the relationship between the microstructure of nanorods and critical current properties for RE123 films with nanorods. To optimize the critical current properties under the magnetic field for RE123 coated conductors with nanorods, precise control of
T
_s
is very important in the production process.