Improvement of Pinning Properties by Refining Gd2O3 Particles Trapped in GdBa2Cu3O7-δ Coated Conductors Fabricated by the RCE-DR Process

In order to improve in-field
J
_c
values of GdBCO CCs fabricated by the reactive co-evaporation by deposition and reaction (RCE-DR) process with the nominal composition of Gd:Ba:Cu = 1:1:2.5, the Gd
₂
O
₃
particles trapped in the GdBCO superconducting matrix were refined by controlling the nucleation and growth temperature of Gd
₂
O
₃
in the liquid phase before the growth of GdBCO film at the same growth conditions of 860 °C in 150 mTorr oxygen pressure. With decreasing the growth temperature of Gd
₂
O
₃
from 860 to 820 °C in the oxygen pressure of 30 mTorr, the average particle size of Gd
₂
O
₃
was monotonously decreased from 125 ± 41 to 73 ± 31 nm. With refining the average particle size of Gd
₂
O
_3,
while
J
_c
in a self-field was monotonously decreased, minimum in-field
J
_c
values were first increased and then decreased again. With lowering the growth temperature of Gd
₂
O
₃
, the gradual decrease of self-field
J
_c
may be mainly attributed to the gradual degradation of both in-plane and out-of-plane textures, the variation of the minimum in-field
J
_c
values might originate mainly from the variation of the stacking fault density, which, however, requires further analysis.