Giant dielectric permittivity with low loss tangent and excellent non−Ohmic properties of the (Na+, Sr2+, Y3+)Cu3Ti4O12 ceramic system

Abstract

The (Na+, Sr2+, Y3+)Cu3Ti4O12 ceramic system was successfully synthesized using the solid-state reaction method; further, its crystal structure and microstructure were studied. The main phase associated with the CaCu3Ti4O12 like-structure was detected. A dense ceramic microstructure with segregation of Cu−rich phase at the grain boundaries (GBs) was observed in the sintered ceramics. A significantly high range of dielectric permittivity (1.63 × 103−2.34 × 104), and a low range of dielectric loss tangent (0.035–0.075) were observed for the sintered (Na1/2Y1/2)1-xSrxCu3Ti4O12 ceramics at x = 0.1 and 0.2. Further, a steep enhancement of non-Ohmic characteristics was achieved along with the high breakdown electric field of ~9.12 kV cm−1 and the nonlinear coefficient of ~84.7 for the (Na1/2Y1/2)0.90Sr0·10Cu3Ti4O12 ceramic sintered at 1060 °C for 18 h. The presence of heterogeneous microstructures, which are comprised of semiconducting grains and insulating GBs with, respectively, conduction activation energies of 0.05–0.09 eV and ~0.6 eV, was confirmed by impedance spectroscopy; the results displayed a large dielectric response and nonlinear electrical properties. The mixing of Cu+/Cu2+/Cu3+ and Ti3+/Ti4+ was confirmed by X−ray photoelectron spectroscopy, suggesting the presence of a semiconducting state inside the grains.