Dielectric and Electrical Properties of CaCu₃Ti₄O₁₂ Ceramics at High Temperatures

Abstract

CaCu ₃ Ti ₄ O ₁₂ (CCTO) ceramics are prepared by the conventional solid-state reaction method under various sintering time conditions. Dielectric properties and complex impedance spectra are investigated from room temperature up to 350°C. The high dielectric permittivity is found to closely relate to the microstructure. High-temperature dielectric dispersion exhibits a large low-frequency response and two Debye-like relaxations. There exist three semicircles in the complex impedance plane. The observed dielectric and electrical properties are ascribed to the polycrystalline structure. The three semicircles are attributed to the contributions of the domain boundaries, the grain boundaries and the domains in the ascending frequency order, respectively. An equivalent electrical circuit model suggested well fits simultaneously the data of dielectric dispersion and complex impedance.

Keywords:

• CCTO
• microstructure
• dielectric dispersion
• complex impedance
• equivalent electrical circuit model

Acknowledgments

This work is financially supported by 973 Program of 2007CB607504, NSFC Grant No. 50572055 and DSRF Grant No. 2005BS04013 of Shandong Province.