Effects of sintering condition on giant dielectric and nonlinear current-voltage properties of Na(1/2)Y(1/2)Cu(3)Ti(3.975)Ta(0.025)O(12) ceramics

The effects of sintering conditions on the microstructure, giant dielectric response, and electrical properties of Na(1/2)Y(1/2)Cu(3)Ti(3.975)Ta(0.025)O(12) (NYCTTaO) were studied. A single phase of Na(1/2)Y(1/2)Cu(3)Ti(4)O(12) and a high density (>98.5%) were obtained in the sintered NYCTTaO ceramics. First–principles calculations were used to study the structure of the NYCTTaO. Insulating grain boundaries (i–GBs) and semiconducting grains (semi–Gs) were studied at different temperatures using impedance and admittance spectroscopies. The conduction activation energies of the semi–Gs and i–GBs were E(g) ≈ 0.1 and E(gb) ≈ 0.6 eV, respectively. A large dielectric constant (ε′ ≈ 2.43–3.89 × 10(4)) and low loss tangent (tanδ ≈ 0.046–0.021) were achieved. When the sintering temperature was increased from 1070 to 1090 °C, the mean grain size slightly increased, while ε′ showed the opposite tendency. Furthermore, the breakdown electric field (E(b)) increases significantly. As the sintering time increased from 5 to 10 h, the mean grain size did not change, whereas ε′ and E(b) increased. Variations in the dielectric response and non–linear electrical properties were primarily described by the intrinsic (E(gb)) and extrinsic (segregation of Na–, Cu–, Ta–, and O–rich phases) properties of the i–GBs based on the internal barrier layer capacitor effect.