A solid ionic conducting material for use in an electrochemical device comprises an oxyhydroxide or hydrated oxide derived from of an oxide with a perovskite, Brownmillerite, layered oxide, and/or K.sub.4CdCl.sub.6 structure, the elemental composition of the initial oxide being selected to provide suitable conduction properties for the derived anhydrous or hydrated oxyhydroxide or hydrated oxide. A method of making such a solid ionic conducting material, including treatment with water, and an electrochemical device incorporating such a solid ionic conducting material (optionally as an electrolyte) are also disclosed.

In an aspect, an M-type ferrite comprises an element Me comprising at least one of Ba, Sr, or Pb; an element Me comprising at least one of Ti, Zr, Ru, or Ir; and an element Me comprising at least one of In or Sc. In another aspect, a method of making the M-type ferrite can comprise milling ferrite precursor compounds comprising oxides of at least Co, Fe, Me, Me, and Me to form an oxide mixture; wherein Me comprises at least one of Ba, Sr, or Pb; Me is at least one of Ti, Zr, Ru, or Ir; and Me is at least one of In or Sc; and calcining the oxide mixture in an oxygen or air atmosphere to form the ferrite.