Search

The role of yttrium doping on the structural and superconducting properties of SmFeAsO $$_{1-x}$$ F $$_x$$ (Sm1111) is studied in detail and is compared with other yttrium-doped RE1111 (RE-rare earth) iron oxypnictide superconductors on the basis of the existing reports. It is found that the partial substitution of lanthanides such as La, Ce, and Nd with yttrium systematically enhances $$T_\mathrm{C}$$ of the system to different levels depending on their crystal ionic radii difference with yttrium. The isovalent substitution of these lanthanides at relatively smaller yttrium ion site causes inner chemical pressure and enhances the $$T_\mathrm{C}$$ . However, yttrium doping does not seem to be beneficial for Sm1111 because of its larger ionic size. [ABSTRACT FROM AUTHOR]