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 (Tc) 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 Tc 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 Tc 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.