Two classes of superconductors discovered in our material research: Iron-based high temperature superconductor and electride superconductor

We discovered two new classes of superconductors in the course of material exploration for electronic-active oxides. One is 12CaO center dot 7Al(2)O(3) crystal in which electrons accomodate in the crystallographic sub-nanometer-sized cavities. This material exhibiting metal-superconductor transition at 0.2 K is the first electride superconductor. The other is iron oxypnicitides with a layered structure. This superconductor is rather different from high T(c) cuprates in several respects. The high T(c) is emerged by doping carriers to the metallic parent phases which undergo crystallographic transition (tetra to ortho) and Pauli para to antiferromagnetic transition at similar to 150 K. The T(c) is robustto impurity doping to the Fe sites or is induced by partial substitution of the Fe(2+) sites with Co(2+) or Ni(2+). This article gives a brief summary of these discoveries and recent advances. (C) 2009 Elsevier B.V. All rights reserved.