Effects of multiple cations and sintering temperature on microstructure and dielectric properties in Na1/2Ln1/2Cu3Ti4O12 (Ln = Sm and Eu) ceramic materials

Abstract

Na1/2Eu1/2Cu3Ti4O12 and Na1/2Sm1/2Cu3Ti4O12 dielectric ceramics were synthesized at different sintering temperatures (950, 975 and 1000 oC) by a solid-state reaction method. Phase structure, cation valence state, and dielectric properties of all sintered ceramics were systematically investigated. When the preparation temperature was changed, the Cu+ ion concentration of (Na+, Eu3+) co-doped ceramics changed faster than that of (Na+, Sm3+) co-doped ceramics. Abnormally high dielectric permittivity ~3.17 Í 104 were accomplished of Na1/2Sm1/2Cu3Ti4O12 ceramic at a sintering temperature 950 oC. However, Na1/2Eu1/2Cu3Ti4O12 and Na1/2Sm1/2Cu3Ti4O12 prepared in high sintering temperature (1000 oC) exhibited a good dielectric stability and low loss tangent (0.061 and 0.102 at 10 Hz, respectively). It was demonstrated that an increasing number of charge carriers induced by the increase of sintering temperature could lead to a competitive coexistence of two polarization mechanisms (surface barrier layer capacitor and internal barrier layer capacitor), further changing the dielectric properties of CaCu3Ti4O12-based ceramics.