Nonlinear electrical properties and giant dielectric response in Na1/3Ca1/3Y1/3Cu3Ti4O12 ceramic

Abstract

A new isostructural CaCu3Ti4O12–type perovskite, Na1/3Ca1/3Y1/3Cu3Ti4O12, was successfully synthesized using a solid state reaction method. In this material, Ca–sites in the CaCu3Ti4O12 structure were occupied by Na+, Ca2+, and Y3+ ions, each at a level of ∼33.3 at.%. The dielectric and non –Ohmic properties were investigated. The mean grain sizes of the Na1/3Ca1/3Y1/3Cu3Ti4O12 ceramics sintered at 1100–1110°C for 10–15h were of about ≈15μm. All of the sintered ceramics exhibited high dielectric permittivities (ε′) and low loss tangents (tanδ). By optimizing sintering conditions, a high ε′≈1.2×104 and low tanδ≈0.04 were achieved. Na1/3Ca1/3Y1/3Cu3Ti4O12 ceramics can exhibit nonlinear current-voltage behavior. The existence of Cu+, Cu3+, and Ti3+ ions was confirmed using an X–ray Absorption Near Edge Structure (XANES) and X–ray photoelectron spectroscopic analyses. The n–type semiconductivity inside the grains was primarily caused by the presence of Ti3+ ions, while the existence of Cu+ and Cu3+ may also have an effect on conduction inside the grains. Using impedance and admittance spectroscopy analyses under different conditions (i.e., varying frequency, temperature and DC bias), the giant dielectric response and nonlinear electrical properties could be well explained based on the internal barrier layer capacitor model.