Significantly improved dielectric properties of tin and niobium co-doped rutile TiO2 driven by Maxwell-Wagner polarization

High-performance giant dielectric properties (HP-GDPs) of acceptor-donor co-doped TiO2 are generally based on effective suppression of the loss tangent (tan delta) and significant enhancement of dielectric permittivity (epsilon '). In this study, a solid state reaction was used to prepare TiO2-based ceramics displaying HPGDPs by co-doping with isovalent SnO2 and Nb2O5 as a donor at different concentrations. The sintered ceramics showed a dense microstructure (> 97 %) and well-dispersed dopants. The grain size slightly increased (from 1.6 to 2.6 mu m) when the co-doping concentration increased from 1 % to 5 %. The ceramic with the optimal composition featured a large epsilon ' = 3.0 x 104 and a small tan delta = 0.012. Furthermore, the small change in its epsilon ' value (by less than +/- 15 % between -55 and 150 degrees C) meets the temperature dependence requirement for application in the X8R capacitor. The HP-GDPs observed here were primarily caused by Maxwell-Wagner polarization at the internal interface with a large resistivity between the semiconducting grains.