Effects of oxide precursors on superconducting properties of polycrystalline SmFeAsO1−xFx

• Polycrystalline SmFeAsO1−xFx samples were prepared by different oxide precursors.
• Phase formation and superconductivity of these samples were comparatively studied.
• Results show that nano-Fe2O3 and As2O3 promote fluorine doping.

A series of polycrystalline SmFeAsO1−xFx samples were synthesized by one-step and two-step method at ambient pressure using different oxide precursors, namely As2O3, Fe2O3 and nano-Fe2O3 powder, as the source of element O. Results of X-ray diffraction and magnetic measurements manifest that starting oxides affected the phase formation and superconducting properties of SmFeAsO1−xFx. As2O3 as oxide precursor contributes to the fast formation of superconducting phase for a short period of sintering time. And samples prepared using As2O3 show higher superconducting transition temperature Tc and more stable fluorine doping level. Compared with Fe2O3, nano-Fe2O3 promotes fluorine doping into the O site. While using Fe2O3 leads to higher level of Fe and SmOF impurities. The critical current density Jcm were derived from magnetic hysteresis loops. Sample prepared using As2O3 shows higher Jcm in low temperature and high magnetic fields.