Very low loss tangent and giant dielectric properties of CaCu_3Ti_4O_(12) ceramics prepared by the sol-gel process

摘要

The pure phase of CaCu_3Ti_4O_(12) (CCTO) powder can be successfully synthesized by the sol-gel process. CCTO ceramic samples were synthesized at different sintering temperatures of 1015 and 1050 ℃ and sintering times of 8 and 10 h. X-ray diffraction results indicated a pure phase for all ceramic samples. Rietveld refinements were adopted for the calculation of lattice constants. Scanning electron microscopy micrographs revealed the effect of sintering conditions on the microstructural evolution of ceramic samples. X-ray absorption near edge spectroscopy was performed to determine the oxidation state of Cu and Ti ions in ceramic samples. The dielectric and non-linear current voltage properties of CCTO ceramic samples were systematically investigated. Interestingly, very low loss tangent (tanδ< 0.017 at 30 ℃ and 1 kHz) and giant dielectric constant (ε'~ 10,942) with temperature coefficients less than ±15% in a wide temperature range of -60 to 125 ℃ were obtained in the CCTO ceramic sample sintered at 1015 ℃ for 10 h (CCTO1-10). This suggests a potential use for CCTO1-10 sample in capacitor applications. All CCTO ceramic samples display non-linear characteristic with nonlinear coefficient (a) and breakdown field (E_b) values in the range of 5.69-11.02 and 1415-4294, respectively.