Giant dielectric behaviour of CaCu3Ti4O12 subjected to post-sintering annealing and uniaxial stress

Abstract

This paper reports the influences of the post-sintering annealing in argonand uniaxial compressive pre-stress on the giant dielectric properties of theCaCu3Ti4O12 ceramics sinteredat 1100 °C in air for 6 and16 h. The CaCu3Ti4O12 ceramicsintered at 1100 °C for6 h exhibited high ε′ of ∼1 × 104 whereasthe CaCu3Ti4O12 ceramicsintered 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 basedon a Maxwell–Wagner model. Post-sintering annealing in argon for 5 h leads to a significant increase inε′ forCaCu3Ti4O12 ceramic sinteredat 1100 °C for 16 h but aslight decrease in ε′ for the CaCu3Ti4O12 ceramicsintered at 1100 °C for6 h. The ε′ of the16 h sintered CaCu3Ti4O12 ceramic after annealing in argon increases with increasing temperatures, and exhibits a peak at about150 °C, which is closely related to the oxygen vacancies. The dielectric behaviour of thisargon-annealed sample follows the UDR law. The dielectric properties of theargon-annealed samples change significantly with the applied compressive stress (theabsolute change can reach 25% at a maximum stress of 130 MPa). However, the changes indielectric properties with the stress in the samples subjected to different sintering timesfollow opposing trends. The mechanisms responsible for this difference are discussed.