Effect of spark plasma sintering process on dielectric properties of CaCu<inf>3</inf> Ti<inf>4</inf> O<inf>12</inf> ceramics

Abstract

CaCu 3 Ti $_{4} O_{12}$ (CCTO) ceramics with high density were fabricated by spark plasma sintering (SPS) method. In order to study the effect of sintering methods on properties of CCTO ceramics, the samples were sintered at different temperatures $(750^{\circ}\mathrm{C}, 800^{\circ}\mathrm{C}$ and $850^{\circ}\mathrm{C})$, and then were annealed in air at $1000^{\circ}\mathrm{C}$ for 3 hours. The crystalline-phase characters and surface morphology of the samples were characterized by XRD and SEM measurements, and XRD pattern revealed the formation of pure cubic perovskite CCTO. The average grain size was measured to be 1.5-2.2}$\mu m and the relative density reached about 98 %. The non-ohmic characteristics, dielectric properties and impedance response of the ceramic samples were studied by precision highvoltage dc power and impedance spectroscopy. For the sample SPS-750, the electric breakdown field was enhanced to 13.05 kV/cm, and the nonlinear coefficient was increased to 5.69. The great enhancement in electric breakdown field was accompanied with the lowest dielectric loss of 0.013 at around 1 kHz. The maximum stored energy density of CCTO was also promoted to 35.21 kJ/m^{3}. The results showed that the dielectric loss of spark plasma sintered CCTO ceramics can be reduced significantly and the current-voltage properties can also be enhanced, which are ascribed to the improvement of grain boundary resistance during the sintering and annealing treatment.