CaCu3Ti4-xRuxO12: Crystal structure, electrical and magnetic properties

Abstract

The CaCu3Ti4O12 belongs to the large ACu3B4O12 family of materials. Crystallographic A site is most often occupied by alkaline-earth metals or lanthanides, while B site is occupied by transition metals. The type of cations that build up the structure strongly affects the properties of these. The CaCu3Ti4O12 has been extensively studied due to its high dielectric permittivity stable over a wide temperature and frequency range (up to 105, for 100-600 K and 102–105 Hz). Because of such characteristics, it has promising application in microelectronics. However, it has been shown that differences in the crystal structure and electrical properties of dielectric ceramics and metallic electrodes, may cause an energy barrier and occurrence of stress on the ceramic-electrode contact which reduces dielectric permittivity. Such stress can be prevented by using dielectric and electrode materials with as much as possible similar crystal structure, especially unit cell parameters. This investigation dealt with detailed structural (XRPD, HRTEM, SAED), dielectric and magnetic study of CaCu3Ti4-xRuxO12 (CCTRO, x = 0, 1 and 4) materials. The results of structural refinement show that in cubic symmetry with space group Im3 , both titanium and ruthenium ions occupied crystallographic B site. Moreover, the variation in stoichiometry slightly affects the value of the unit cell parameters but changes electrical properties of studied material. Thus, substitution of even one atom of Ru in CaCu3Ti4-xRuxO12 unit cell is enough to change material properties from dielectric to conductor solving the problem of stress appearance on the contact layer of dielectric/electrode in capacitors.