Abstract
The effects of DC bias on the dielectric and electrical properties of co-doped (In1/2Nb1/2)(x)Ti1-xO2 (IN-T), where x = 0.05 and 0.1, and single-doped Ti0.975Nb0.025O2 ceramics are investigated. The low-frequency dielectric permittivity (epsilon') and loss tangent of IN-T ceramics with x = 0.05 and 0.1 are greatly enhanced by applying a DC bias at 40 and 20 V, respectively, whereas the relatively high-frequency epsilon' remains unchanged. The induced low-frequency Maxwell-Wagner polarization completely vanishes by immediately applying no DC bias. After overload limited measurement, this polarization permanently emerges without DC bias, whereas the primary polarization remains unchanged. Using combined Z '' and M '' spectroscopic plots, it is found that the strongly induced-polarizations are contributed from the combination effects of the sample-electrode contact and resistive outer surface. Very high performance of the colossal permittivity in IN-T ceramics is attributed to the formation of a resistive outer-surface layer and insulating grain boundaries. These results not only provide important insights into the origins of the colossal dielectric response in the IN-T ceramic system, but are also important for deciding the doping conditions of TiO2-based materials for practical applications.
