Superconductivity and mechanical properties for LaFe_1-xZn _xAsO_0.85F_0.15

LaFe_1-xZn_xAsO_0.85F_0.15 composites were synthesized by solid state reaction in order to improve the mechanical properties while trying to keep the superconductivity. XRD results indicate that LaFe_1-xZn_xAsO_0.85F_0.15 are series of superconducting composites composed of LaFeAsO _0.85F_0.15 and LaZnAsO_0.85F_0.15. LaFe_1-xZn_xAsO_0.85F_0.15 still exhibits superconductivity up to Zn fraction as high as 80%. The critical temperature T_c slightly decreases from 26.2 K for LaFeAsO _0.85F_0.15 to 23.9 K for LaFe_0.2Zn _0.8AsO_0.85F_0.15, which means that the superconductivity can be maintained if 20% of the superconducting phase exists in the composite. In addition, the mechanical properties of LaFe _1-xZn_xAsO_0.85F_0.15 including micro-hardness, Young's modulus and fracture toughness have been significantly improved in the composite as compared to the Zn free sample. Therefore, we conclude the mechanical properties of the LaFeAsO system, and by extension of other systems, can be enhanced by introducing a second phase without deteriorating the superconductivity.