The superconducting properties of polycrystalline Sr0.6K0.4Fe2As2 were strongly influenced by Ag doping(Supercond.Sci.Technol.23(2010) 025027).Ag addition is mainly dominated by silver diffusing,so the annealing process is one of the essential factors to achieve high quality Ag doped Sr0.6K0.4Fe2As2.In this paper,the optimal annealing conditions were studied for Ag doped Sr0.6K0.4Fe2As2 bulks prepared by a one-step solid reaction method.It is found that the annealing temperature has a strong influence on the superconducting properties,especially on the critical current density Jc.As a result,higher heat treatment temperature(~900℃) is helpful in diffusing Ag and reducing the impurity phase gathered together to improve the grain connectivity.In contrast,low-temperature sintering is counterproductive for Ag doped samples.These results clearly suggest that annealing at ~900℃ is necessary for obtaining high Jc Ag-doped samples.
ZHANG ZhiYu,WANG Lei,QI YanPeng,GAO ZhaoShun,WANG DongLiang,ZHANG XianPing & MA YanWei* Key Laboratory of Applied Superconductivity,Institute of Electrical Engineering,Chinese Academy of Sciences,Beijing 100190,China
The crystal structure and the superconductivity for samples Mg(B 1-x C x) 2 (0 ≤ x ≤ 0.09) prepared by a hybrid microwave synthesis have been investigated.The starting material B 10 C is also obtained by using the microwave method.The carbon can distribute uniformly in the Mg(B 1-x C x) 2 samples because boron and carbon are mixed on an atomic scale in the staring material B 10 C.The dependences of both lattice parameters and superconducting transition temperature T c on carbon content accord with those reported in the literature.The upper critical field H c2 at 20 K can be enhanced from about 4.3 T for x=0 to 10 T for x=0.05.The critical current density J c of Mg(B 0.95 C 0.05) 2 is 1.05 × 10 4 A/cm 2 at 20 K and 1 T.
