Giant dielectric behaviour of CaCu₃Ti₄O₁₂subjected to post-sintering annealing and uniaxial stress

Abstract

This paper reports the influences of the post-sintering annealing in argon and uniaxial compressive pre-stress on the giant dielectric properties of the CaCu3Ti4O12 ceramics sintered at 1100 °C in air for 6 and 16 h. The CaCu3Ti4O12 ceramic sintered at 1100 °C for 6 h exhibited high ε′ of ∼1 × 104 whereas the CaCu3Ti4O12 ceramic sintered at 1100 °C for 16 h possessed one order of magnitude higher dielectric constant (ε′∼2 × 104). The dielectric behaviour of both samples exhibits Debye-like relaxation, and can be explained based on a Maxwell–Wagner model. Post-sintering annealing in argon for 5 h leads to a significant increase in ε′ for CaCu3Ti4O12 ceramic sintered at 1100 °C for 16 h but a slight decrease in ε′ for the CaCu3Ti4O12 ceramic sintered at 1100 °C for 6 h. The ε′ of the 16 h sintered CaCu3Ti4O12 ceramic after annealing in argon increases with increasing temperatures, and exhibits a peak at about 150 °C, which is closely related to the oxygen vacancies. The dielectric behaviour of this argon-annealed sample follows the UDR law. The dielectric properties of the argon-annealed samples change significantly with the applied compressive stress (the absolute change can reach 25% at a maximum stress of 130 MPa). However, the changes in dielectric properties with the stress in the samples subjected to different sintering times follow opposing trends. The mechanisms responsible for this difference are discussed.

Electrical properties and microstructural characteristics of nonstoichiometric CaCu3xTi4O12 ceramics

“…Both CCTO crystal and ceramics exhibit a giant dielectric permittivity of about 10 4 -10 6 at room temperature and fine thermal stability over a wide temperature range from 100 to 600 K [1][2][3][4][5][6]. This material does not undergo any structural change over the same temperature range, although its dielectric constant abruptly decreases to less than 100 below 100 K, showing a Debye-type relaxation.…”

“…This material does not undergo any structural change over the same temperature range, although its dielectric constant abruptly decreases to less than 100 below 100 K, showing a Debye-type relaxation. Several explanations for the origin of the colossal dielectric property of CaCu 3 Ti 4 O 12 material have been proposed and they are attributed to either intrinsic or extrinsic effects [5,7,8]. More investigations tend to indicate that the high dielectric constant originates from the extrinsic effect such as internal barrier layer capacitor (IBLC) [9][10][11], contact-electrode effect [12,13] and special inhomogeneity of local dielectric response [14,15].…”

Dielectric properties of Nb-doped CaCu3Ti4O12 electroceramics measured at high frequencies

“…The CCTO is very sensitive to processing parameters which will affect its electrical properties like dielectric constant. Extensive investigation has been made to identify the origin of the colossal dielectric property of CCTO [4][5][6]. This understanding will help the processing of CCTO to achieve certain electrical properties.…”

Anomalous change in dielectric constant of CaCu3Ti4O12 under violet-to-ultraviolet irradiation

“…20. CCTO powders were sintered in air at 1050 C for 6 h. From scanning-electron-microscopy micrographs, the CCTO ceramics were found to have average grain sizes of approximately 2-5 lm in diameter.…”