Superconductivity in 1111-type CaFeAsF1-xHx induced by selective hydrogen elimination

The difference in thermal stability of F- and H- in 1111-type iron based superconductors, allows selective hydrogen elimination from non-superconductive CaFeAsF0.8H0.2 by thermal annealing. The analyzed chemical composition of the resulting samples indicates that incorporated hydrogen was selectively eliminated by thermal annealing at 553 K for 72 hours. The resulting hydrogen-eliminated sample shows bulk superconductivity with Tc = 29 K. This technique may be used for indirect electron doping for AeFeAeF (Ae; alkali-earth metal) iron based superconductor described by CaFeAsF1-xHx => CaFeAsF1-x + xe- + 1/2xH2.