Dielectric properties of (Eu,Ca)Cu3Ti4O12 ceramics prepared by a sol-gel method

Abstract

CaCu3Ti4O12 perovskite-type phase possesses promising dielectric properties; however, the giant permittivity phenomenon in this material has not been satisfactorily described yet. Eu with similar electronegativity and ionic radius as Ca was selected for testing of partly and completely substituted materials. Here, we prepared a series with a composition of CaCu3Ti4O12, Eu0.4Ca0.6Cu3Ti4O12 and EuCu3Ti4O12. A sol-gel method was used to synthetize precursors, followed by sintering in a temperature range of 1000 °C-1120 °C. Europium was substituted in full stoichiometry of CaII with the aim to observe whether i) EuII is stabilized in the perovskite structure and/or ii) possible secondary phases induced by the excess of EuIII positively affect the dielectric characteristics. Samples were characterized by XPS, XRD, SEM. Influence of the microstructure and phase composition on the dielectric properties of the samples (also in relation to the sintering temperature) is discussed. Secondary phases and microstructure played an important role in improving the permittivity values. The obtained values of permittivity measured at room temperature are giant up to higher frequencies, but differ significantly for some individual compositions.