RAMAN AND DIELECTRIC SPECTRA OF CaCu₃Ti_3.9O₁₂ CERAMICS

Abstract

To investigate the physical origin of high dielectric CaCu3Ti4.0O12 (CCTO), we have prepared the Ti-deficiency CaCu3Ti3.9O12 (CCTO39) ceramics, using the traditional solid state reaction method. Raman spectroscopy shows the damping of Fg(3) mode, i.e. the O-Ti-O antistretching motion, is higher in CCTO39 than in CCTO and suggests that the antistretching motion may be over damped in the CCTO39 samples. The dielectric spectrum presents that, the relative dielectric constant, ε′, reduces from ∼ 105 (CCTO) to ∼ 103 (CCTO39) above 150 K, and at the lowest temperature it reduces from ∼ 220 (CCTO) to ∼ 140 (CCTO39). The dissipation peaks are 10-foldly depressed. Their characteristic relaxation frequencies may not obey the Arrhenius law but a tentative relation. All the experiments suggest that the dielectric relaxation is related to the mutually correlated motion of Ti ions and defects.