Synthesis and characterization of (Ba, Sr)Fe2(As, P)2 iron pnictide superconductors

Abstract We prepared polycrystalline samples with nominal compositions of (Ba 0.5 Sr 0.5 )Fe 2 (As 1− x P x ) 2 ( x  = 0. 2, 0.3, 0.35, 0.4, 0.5, 0.6). Nearly single-phase samples were successfully obtained. Rietveld refinements of the powder XRD data revealed that the cell volume was gradually reduced with increasing the P content x . Comparing with the reported data for P-substituted Ba122 (Ba122:P) and Sr122 (Sr122:P), the P-substituted (BaSr)122 exhibited intermediate structural properties. The structure of the Fe 2 (As, P) 2 block was almost identical regardless of different alkaline earth elements. The sample with x  = 0.4 showed the highest T c of 29 K, being nearly identical to those of Ba122:P and Sr122:P.