High dielectric constant in ACu3Ti4O12 and ACu3Ti3FeO12 phases

High dielectric constants have been found in oxides of the type ACu(3)Ti(4)O(12). The most exceptional behavior is exhibited by CaCu3Ti4O12, which shows a dielectric constant at 1 kHz of about 12,000 that is nearly constant from room temperature to 300 degrees C, The cubic structure of these materials is related to that of perovskite (CaTiO3), but the TiO6 octahedra are tilted to produce a square planar environment for Cu2+. The CaCu3Ti4O12 structure down to 35 K has been examined by neutron powder diffraction. The structure remains cubic and centric, Most compositions of the type A(2/3)Cu(3)Ti(4)O(12) (A = trivalent rare earth or Bi) show dielectric constants above 1000, The dielectric properties of isostructural compounds of the type ACu(3)Ti(3)FeO(12) are also presented. (C) 2000 Academic Press.