High Dielectric Constant and Dielectric Relaxations in LaCuTiO Ceramics.

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