Effects of multiple cations and sintering temperature on microstructure and dielectric properties in Na 1/2 Ln 1/2 Cu 3 Ti 4 O 12 (Ln = Sm and Eu) ceramic materials

Na 1/2 Eu 1/2 Cu 3 Ti 4 O 12 and Na 1/2 Sm 1/2 Cu 3 Ti 4 O 12 dielectric ceramics were synthesized at different sintering temperatures (950, 975 and 1000 °C) 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 + , Eu 3+ ) co-doped ceramics changed faster than that of (Na + , Sm 3+ ) co-doped ceramics. Abnormally high dielectric constants of ~ 3.17 × 10 4 and ~ 1.06 × 10 4 (at 10 Hz and 303 K) were achieved in Na 1/2 Sm 1/2 Cu 3 Ti 4 O 12 and Na 1/2 Eu 1/2 Cu 3 Ti 4 O 12 ceramics prepared at 950 °C, respectively. However, Na 1/2 Sm 1/2 Cu 3 Ti 4 O 12 and Na 1/2 Eu 1/2 Cu 3 Ti 4 O 12 prepared in high sintering temperature (1000 °C) exhibited a good frequency stability of dielectric permittivity. 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 CaCu 3 Ti 4 O 12 -based ceramics.