Xingquan Zhang

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

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 AlxNb0.03Ti0.97−xO2 (x = 0, 0.01, 0.03 and 0.05) ceramics. CP with low dielectric loss was found in AlxNb0.03Ti0.97−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 AlxNb0.03Ti0.97−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.

Colossal dielectric permittivity in (Al + Nb) co-doped rutile SnO2 ceramics with low loss at room temperature

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Alu2009+u2009Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 103) and low dielectric losses (0.015u2009<u2009tan δu2009<u20090.1) in a wide range of frequencies and at temperatures from 140 to 400u2009K. Al doping can effectively modulate the dielectric behavior by increasing the grain and grain boundary resistances. The large differences in the resistance and conductive activation energy of the grains and grain boundaries suggest that the CP in co-doped SnO2 ceramics can be attributed to the internal barrier layer capacitor effect.