(Al3+, Nb5+) co–doped CaCu3Ti4O12: An extended approach for acceptor–donor heteroatomic substitutions to achieve high–performance giant–dielectric permittivity

Abstract

Substitution of (Al3+, Nb5+) co–dopants into TiO6 octahedral sites of CaCu3Ti4O12 ceramics, which were prepared by a solid state reaction method and sintered at 1090°C for 18h, can cause a great reduction in a low–frequency loss tangent (tanδ≈0.045–0.058) compared to those of Al3+ or Nb5+ single–doped CaCu3Ti4O12. Notably, very high dielectric permittivities of 2.9−4.1×104 with good dielectric–temperature stability are achieved. The room–temperature grain boundary resistance (Rgb≈0.37–1.17×109Ω.cm) and related conduction activation energy (Egb≈0.781–0.817eV), as well as the non–Ohmic properties of the co–doped ceramics are greatly enhanced compared to single–doped ceramics (Rgb≈104–106Ωcm and Egb≈0.353–0.619eV). The results show the importance of grain boundary properties for controlling the nonlinear–electrical and giant–dielectric properties of CaCu3Ti4O12 ceramics, supporting the internal barrier layer capacitor model of Schottky barriers at grain boundaries.