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.