... Inorganic Synthesis . ... Four families of superconductors were obtained and characterized; thay are the so-called family of 1111 with the general formula LnOFeAs (Ln – rare earth metal), the 122 family – AEFe 2 As 2 (AE = Ca, Sr, Ba and Eu (II)), the 111 family – AFeAs (A = Li, Na), and the 011 family – FeSe. ... In the 1111 phases, such blocks have the fluorite structure (LnO); in 122 they are alkaline earth metal cations AE(2), in phases of the 111 family they are alkali metal cations Li and Na. ...