Effects of sintering condition on giant dielectric and nonlinear current-voltage properties of NaYCuTiTaO ceramics.

The effects of sintering conditions on the microstructure, giant dielectric response, and electrical properties of NaYCuTiTaO (NYCTTaO) were studied. A single phase of NaYCuTiO 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 ≈ 0.1 and E ≈ 0.6 eV, respectively. A large dielectric constant (ε' ≈ 2.43-3.89 × 10) 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) increases significantly. As the sintering time increased from 5 to 10 h, the mean grain size did not change, whereas ε' and E increased. Variations in the dielectric response and non-linear electrical properties were primarily described by the intrinsic (E) and extrinsic (segregation of Na-, Cu-, Ta-, and O-rich phases) properties of the i-GBs based on the internal barrier layer capacitor effect.