High Dielectric Constant and Dielectric Relaxations in La(2/3)Cu(3)Ti(4)O(12) Ceramics

La(2/3)Cu(3)Ti(4)O(12) ceramics were prepared by the same method of solid-state reaction as CaCu(3)Ti(4)O(12) ceramics. The structure and dielectric responses for La(2/3)Cu(3)Ti(4)O(12) and CaCu(3)Ti(4)O(12) ceramics were systematically investigated by X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, and impedance analyzer. Compared with CaCu(3)Ti(4)O(12) ceramics, La(2/3)Cu(3)Ti(4)O(12) ceramics with higher density and refined grain exhibit a high dielectric constant (ε′ ~ 10(4)) and two dielectric relaxations in a wide temperature range. The dielectric relaxation below 200 K with an activation energy of 0.087 eV in La(2/3)Cu(3)Ti(4)O(12) ceramics is due to the polyvalent state of Ti(3+)/Ti(4+) and Cu(+)/Cu(2+), 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 La(2/3)Cu(3)Ti(4)O(12) ceramics both move to lower temperatures, which can be associated with the enhanced polyvalent structure in La(2/3)Cu(3)Ti(4)O(12) ceramics. Such high dielectric constant ceramics are also expected to be applied in capacitors and memory devices.