Na1/3Ca1/3Bi1/3Cu3Ti4O12: A new giant dielectric perovskite ceramic in ACu3Ti4O12 compounds

A new approach to achieve a novel perovskite ceramic compound, ACu3Ti4O12, is presented. A-sites in the ACu3Ti4O12 structure were occupied by Na+, Ca2+, and Bi3+ each at a level of ∼33.3 at.%, leading to formation of Na1/3Ca1/3Bi1/3Cu3Ti4O12. This ceramic exhibited a low loss tangent (tan δ ∼ 0.038) and a high ɛ′ value of ∼2.5 × 104 at 1 kHz with good temperature stability. The high-frequency dielectric relaxation behavior showed activation energies of 0.110–0.121 eV. Nonlinear J–E characteristics were observed, indicating the existence of Schottky barriers at grain boundaries. Valence states of Cu cations (i.e., Cu+, Cu2+, and Cu3+) in Na1/3Ca1/3Bi1/3Cu3Ti4O12 ceramic were investigated using X-ray photoelectron spectroscopy. Impedance spectroscopy analysis revealed that Na1/3Ca1/3Bi1/3Cu3Ti4O12 was electrically heterogeneous and comprised of semiconducting grains and insulating grain boundaries. Interfacial polarization at the insulating layer of grain boundaries was suggested to be the origin of this high dielectric response.