Significantly Improved Colossal Dielectric Properties and Maxwell-Wagner Relaxation of TiO-Rich NaYCuTiO Ceramics.

In this work, the colossal dielectric properties and Maxwell-Wagner relaxation of TiO-rich NaYCuTiO ( = 0-0.2) ceramics prepared by a solid-state reaction method are investigated. A single phase of NaYCuTiO is achieved without the detection of any impurity phase. The highly dense microstructure is obtained, and the mean grain size is significantly reduced by a factor of 10 by increasing Ti molar ratio, resulting in an increased grain boundary density and hence grain boundary resistance (). The colossal permittivities of ' ~ 0.7-1.4 × 10 with slightly dependent on frequency in the frequency range of 10-10 Hz are obtained in the TiO-rich NaYCuTiO ceramics, while the dielectric loss tangent is reduced to tanδ ~ 0.016-0.020 at 1 kHz due to the increased . The semiconducting grain resistance () of the NaYCuTiO ceramics increases with increasing , corresponding to the decrease in Cu/Cu ratio. The nonlinear electrical properties of the TiO-rich NaYCuTiO ceramics can also be improved. The colossal dielectric and nonlinear electrical properties of the TiO-rich NaYCuTiO ceramics are explained by the Maxwell-Wagner relaxation model based on the formation of the Schottky barrier at the grain boundary.