Development of new superconductors with layered mixed anion compounds

Abstract

Layered mixed anion compounds are materials containing plural anions. These systems are less studied compared to single anion compounds. We have established several guidelines to synthesize these compounds, and developed several iron-based superconductors using the guidelines. The iron-based superconductors having perovskite-type blocking layers have a variety of crystal structures and constituent elements compared to other iron-based superconductors. Moreover, compounds such as (Ca,RE)FeAs₂ have mixed valence anions, and peculiar physical properties such as a low anisotropy parameter γ while the structural anisotropy of the compound is rather high. Layered mixed anion compounds also have other functionalities such as transparent conductors and luminescence, and the development of materials and functionalities are still in progress.