Effect of Zn2+ and Nb5+ co-doping ions on giant dielectric properties of rutile-TiO2 ceramics

Abstract The dielectric properties of Zn 2+ and Nb 5+ co–doped rutile–TiO 2 (ZNTO) ceramics with various dopant concentrations prepared by a solid state reaction method are investigated. Highly dense microstructure and homogeneous dispersion of co–dopants are achieved in all sintered ZNTO ceramics. The presence of Ti 3+ and oxygen vacancies is confirmed using X–ray photoelectron spectroscopy. By optimizing dopant concentration, greatly enhanced dielectric permittivity of ≈5×10 4 and very low dielectric loss tangents of ≈0.03 at a low frequency are achieved. Impedance spectroscopy analysis reveals that the ZNTO ceramics are electrically heterogeneous, consisting of semiconducting and insulating phases. The low–frequency dielectric permittivity and dielectric loss tangent increase with increasing co-dopant concentration, corresponding to the enhancement of free charge carriers inside the grains and a decrease in the total resistance of the insulating phases, respectively. The giant dielectric properties should be associated with the interfacial polarization at internal insulating barriers.