Enhanced Pinning Properties of GdBa2Cu3O7-δ Films With the Gd 2O3 Nanoparticles

We tried to optimize the pinning properties of GdBa
₂
Cu
₃
O
_7-δ
(GdBCO) films with the Gd
₂
O
₃
nanoparticles. The GdBCO films with the Gd
₂
O
₃
contents of 0, 2, 5, 7, and 10 mol% were fabricated on CeO
₂
-buffered MgO (100) substrate by pulsed laser deposition. Among these samples, 5 mol% (= 2.2 vol%) Gd
₂
O
₃
-doped GdBCO film exhibited the highest critical current density (J
_c
) values compared with other samples at temperatures of 20 and 40 K for B//c, and it also showed the maximum pinning force density (F
_p,max
) value of 119 GN/m
³
near 3.8 T at 20 K, indicating that 5 mol% Gd
₂
O
₃
is the optimum doping content below 40 K. However, the Gd
₂
O
₃
nanoparticles were ineffective for flux pinning at higher temperatures (>65 K). Analysis by transmission electron microscopy for this sample revealed that the Gd
₂
O
₃
nanoparticles of ~20 nm in diameter randomly dispersed in the GdBCO matrix. This peculiar pinning characteristics of 2.2 vol% Gd
₂
O
₃
-doped GdBCO film in comparison with 2.5 vol% Y
₂
O
₃
-doped YBCO film [P. Mele et al. 2007] are attributable to more severe degradation of Tc,zero and also to much larger particle size of Gd
₂
O
₃
compared with that of Y
₂
O
₃
nanoparticles (~8 nm).