MgF 2 doping of SmFeAsO superconductors prepared by mechanical alloying and rapid annealing

Magnesium and fluorine codoped Sm1-x/2Mgx/2-FeAsO1-xFx (x = 0 - 0.3) superconductors were prepared by the process of mechanical alloying and subsequent rapid sintering. The transition temperature (T-c) increases with x and reaches 53.3 K at x = 0.3, accompanied by decreased lattice parameters. Electron-type conduction in the MgF2-doped samples was found by Hall-effect measurements. The higher T-c value of Sm1-xMgx/2FeAsO1-xFx was attributed to the larger disorder and a higher internal pressure from the Sm and O sites, similar to the case of (Ln(1-x)M(x))(2)CuO4 superconductors (where Ln is a rare-earth element and M = Ca, Sr, Ba).