Effect of Li doping on the superconducting properties of single domain GdBCO bulks fabricated by the top-seeded infiltration and growth process

Single domain GdBCO bulk superconductors have been fabricated by the top-seeded infiltration and growth process (Gd+011 TSIG) with solid phase compositions of (1-x)(Gd₂O₃+1.2BaCuO₂)+xLi₂CO₃, (x=0, 0.04, 0.08, 0.10, 0.12, 0.16 wt%). The effect of Li₂CO₃ doping on the growth morphology, microstructure, levitation force, trapped field and critical temperature (T_c) of single domain GdBCO bulks have also been investigated based on these samples. The results show that the single-domain GdBCO bulks can be fabricated when x is in the range of 0–0.16 wt%. The size and distribution of Gd211 particles are not influenced by the Li₂CO₃ doping in the samples. The T_c of the samples decrease from 92.5 K (x=0 wt%) to 89.5 K (x=0.16 wt%) when x increases. The decreasing trend of T_c was caused by the substitution of Li⁺ on Cu²⁺ site in the GdBCO crystal. Both of the levitation forces and trapped fields of the samples increase first and then decrease with the increase of x; both of the largest levitation force of 38.5 N（77 K，0.5 T） and the largest trapped field of 0.31 T（77 K，0.5 T） are obtained in the sample when x=0.10 wt%. These results show that appropriate Li doping is an effective way to enhance the flux pinning force and the other physical properties of GdBCO bulk superconductors fabricated by the Gd+011 TSIG method.