We have succeeded in fabricating the first Ce doped GdBa₂Cu₃O_y films with high J_c by the fluorine-free MOD method. From our previous study, it is confirmed that La doping is very effective in promoting crystallization and crystal growth of the superconducting phase. Therefore, we have fabricated the Ce and La co-doped films and studied the J_c properties. T_c for non-doped film indicated around 90 K and those for Ce and La co-doped ones were slightly larger. At 77.3 K under 0 T, the J_c for 2.0 mol% Ce and 1.0 mol% La co-doped film achieved 3.28 MAcm^-2 and increased by about 55% than only 2.0mol% Ce-doped. At 77.3K under 1.0T, that achieved 0.267 MAcm^-2 and increased by about 67% than only 2.0mol% Ce-doped. By Ce doping, F_p also increased and the peak of F_p shifted to the high magnetic field side. Furthermore, we estimated the elementary pinning force (f_p) according to the single vortex theory. f_p indicated 4.23 Nm^-1 and increased by about 60 % at 4.2 K for 2.0 mol% Ce and 1.0 mol% La co-doped film than that for only 2.0mol% Ce-doped. We also have studied the optimization of the heat treatment condition and investigated the properties of Ce and La co-doped film to improve J_c further.

Keywords: artificial pinning centers, metal organic deposition, fluorine-free metal organic deposition, GdBa2Cu3Oy