Superconductivity at 28.3 and 17.1 K in (Ca4Al2O6-y)(Fe2Pn2) (Pn=As and P)

Here we report on discovery of (Ca4Al2O6-y)(Fe(2)Pn(2)) (Pn=As and P) [Al-42622(Pn)] superconductor using high-pressure synthesis technique. Al-42622 (Pn) exhibit superconductivity for both Pn=As and P with the transition temperatures of 28.3 K and 17.1 K, respectively. The a-lattice parameters of Al-42622(Pn) (a=3.713 angstrom and 3.692 angstrom for Pn=As and P, respectively) are smallest among the iron-pnictide superconductors. Correspondingly, Al-42622(As) has the smallest As-Fe-As bond angle (102.1 degrees)and the largest As distance from the Fe planes (1.500 angstrom). (C) 2010 American Institute of Physics. [doi:10.1063/1.3508957]