Non-stoichiometry influence on dielectric properties of CaCu3Ti4O12 based ceramics

Abstract

CaCu3Ti4O12 (CCTO) based ceramics with variations in the amount of CuO and TiO2 were prepared using powders synthesized via the coprecipitation method and calcined in two stages. The ceramics, denoted as CaCuxTiyO12, where 2.70 ≤ x ≤ 3.00 and 3.25 ≤ y ≤ 4.00 (CCxTyO), were sintered using conventional method at 1150 °C for 2 h. The evaluation of the structure, microstructure, and semiquantitative microanalyses of the CCxTyO ceramics was conducted. Impedance spectroscopy, over the frequency range of 20.0 Hz to 5.0 MHz, was performed to analyze the dielectric constant (εr′), dielectric loss factor (tanδ), impedance (Z*) and electrical modulus (M*) of the ceramics. The correlation between the variations in the amounts of CuO and TiO2, microstructure, and dielectric properties of ceramics was explored. It was observed that stoichiometric variation of the amounts of CuO and TiO2 could significantly impact in the grain growth, phase content, and consequently in dielectric properties of the ceramics. Among the ceramics studied, the CC2.90T3.75O ceramic exhibited the largest amount of CaCu3Ti4O12 (98.4%) and D50 (8.38 µm), the highest dielectric constant (εr′ = 26,880) and the lower tanδ (0.063) at 1 kHz.