The contribution of doped-Al to the colossal permittivity properties of AlxNb0.03Ti0.97−xO2 rutile ceramics

Abstract

The search for colossal permittivity (CP) materials continues to attract considerable interest motivated by not only academic research but also potential applications. Very recently, CP with low dielectric loss was reported in In + Nb co-doped rutile TiO₂ polycrystalline ceramics. However, the mechanism of CP in this material system and the effect of doping ions are still unclear. Here, we investigated the dielectric properties of Al_xNb_0.03Ti_0.97−xO₂ (x = 0, 0.01, 0.03 and 0.05) ceramics. CP with low dielectric loss was found in Al_xNb_0.03Ti_0.97−xO₂ samples (x ≤ 0.03). Once the amount of Al-doping exceeds Nb, the CP disappears. The change in dielectric response with varying Al-doping concentration and Ti³⁺ concentration together with the conductive activation energy in Al_xNb_0.03Ti_0.97−xO₂ ceramics clearly suggest that the CP mechanism in co-doped TiO₂ ceramics could be attributed to the internal barrier layer capacitor effect. We believe that our research provides comprehensive guidance for the development of CP materials.