Electrical and dielectric properties of Na_1/2La_1/2Cu₃Ti₄O₁₂ ceramics prepared by high energy ball-milling and conventional sintering

We report on the measurements of the electrical and dielectric properties of Na_1/2La_1/2Cu₃Ti₄O₁₂ (NLCTO) ceramics prepared by high energy ball-milling and conventional sintering without any calcination steps. The x-ray powder diffraction analysis shows that pure perovskite-like CCTO phase is obtained after sintering at 1025℃-1075℃. Higher sintering temperatures result in multi-phase ceramics due to thermal decomposition. Scanning electron microscope observations reveal that the grain size is in a range of ~3 μm-5 μm for these ceramics. Impedance spectroscopy measurements performed in a wide frequency range (1 Hz-10 MHz) and at various temperatures (120 K-470 K) are used to study the dielectric and electrical properties of NLCTO ceramics. A good compromise between high ε' (5.7×10³ and 4.1×10³ at 1.1 kHz and 96 kHz, respectively) and low tanδ (0.161 and 0.126 at 1.1 kHz and 96 kHz, respectively) is obtained for the ceramic sintered at 1050℃. The observed high dielectric constant behavior is explained in terms of the internal barrier layer capacitance effect.