High Dielectric Constant and Dielectric Relaxations in La2/3Cu3Ti4O12 Ceramics

Abstract

La2/3Cu3Ti4O12 ceramics were prepared by the same method of solid-state reaction as CaCu3Ti4O12 ceramics. The structure and dielectric responses for La2/3Cu3Ti4O12 and CaCu3Ti4O12 ceramics were systematically investigated by X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, and impedance analyzer. Compared with CaCu3Ti4O12 ceramics, La2/3Cu3Ti4O12 ceramics with higher density and refined grain exhibit a high dielectric constant (ε′ ~ 104) and two dielectric relaxations in a wide temperature range. The dielectric relaxation below 200 K with an activation energy of 0.087 eV in La2/3Cu3Ti4O12 ceramics is due to the polyvalent state of Ti3+/Ti4+ and Cu+/Cu2+, while the dielectric relaxation above 450 K with higher activation energy (0.596 eV) is due to grain boundary effects. These thermal activated dielectric relaxations with lower activation energy in La2/3Cu3Ti4O12 ceramics both move to lower temperatures, which can be associated with the enhanced polyvalent structure in La2/3Cu3Ti4O12 ceramics. Such high dielectric constant ceramics are also expected to be applied in capacitors and memory devices.