In this paper, Ta-doped Bi 2/3 Cu 3 Ti 4 O 12 (BCTO) ceramics are prepared by solid-state method. Phase structure, microstructure, optical, dielectric, and non-Ohmic properties of all samples are systematically investigated. Cu/Ta-rich phases at grain boundaries (GB) together with defects affect the microstructure, causing grain size and compactness to increase first and then decrease. Moreover, Ta doping increases the optical band gap of BCTO from 4.03 to 4.25 eV as well as the GB activation energy and GB barrier. An increase in dielectric constant (Ɛ r ), nonlinear coefficient (α) and breakdown field (E b ), and a decrease in the dielectric loss (tanδ) are observed in Ta-doped BCTO ceramics. The improvement in dielectric and non-Ohmic properties can be attributed to the internal barrier layer caused by GB Schottky barrier structure. In particular, Bi 2/3 Cu 3 Ti 3.95 Ta 0.05 O 12 ceramic exhibits the high Ɛ r of ∼45997 and the low tanδ of ∼0.035 at 10 kHz along with α of ∼5.62, and E b of ∼3.45 kV/cm. The temperature-independent (-110-210 °C) dielectric response confirms that temperature stability of specimens increases with doping. These results suggest that improved optical, dielectric, and non-Ohmic properties in Bi 2/3 Cu 3 Ti 4 O 12 can be achieved simultaneously via defect engineering.
It is always a challenging problem to simultaneously obtain a large dielectric constant ( ɛ ′), low dielectric loss (tan δ ), and good nonlinear performance in the ACu 3 Ti 4 O 12 (ACTO) ceramic family. In this study, Y 3+ -doped Bi 2/3 Cu 3 Ti 4 O 12 ceramics with a giant ɛ ′, low tan δ , high breakdown field strength ( E b ), and high nonlinearity coefficient ( α ) were successfully prepared via the solid-state method. The (Bi 0.5 Y 0.5 ) 2/3 Cu 3 Ti 4 O 12 ceramic exhibited a huge ɛ ′ (∼12660), very small tan δ (∼0.019), high E b (∼15.7 kV/cm), high α (∼7.61), and high energy storage density (∼140.2 mJ/cm 3 ). The impedance spectra and electrical modulus results show that the dielectric properties of the prepared ceramics follow the internal barrier layer capacitor model. The enhanced tan δ and improved nonlinear properties of the doped samples are associated with the increased grain boundary resistance and Schottky barrier. These results provide important clues and valuable insights for realizing bifunctional ACTO materials with a giant ɛ ′, low tan δ , and excellent nonlinear properties.
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