Origin of the dielectric abnormities and tunable dielectric properties in doped KTN single crystals

Abstract

The dielectric properties of (Fe,Li)-codoped KTa1−xNbxO3 single crystals have been measured, and the origin of the dielectric abnormities was discussed in detail. In the low temperature range of 20–100 K for each of the samples, the relaxation R1 is attributed to the electrons-activating/freezing in the defect-dipoles while the dielectric abnormity is contributed by the relaxation R1 and the two phase transitions (PR-O and PO-T). The relaxation R2 in the range of 100–200 K is likely due to the reorientation of the dipolar structure Fe3+-Oi2− as well as the formation of a small number of non-localized polaronic particles. In the high temperature range of 200–450 K, controlling the temperature interval between the first-order phase transition P1 and the diffuse transition P2 could make permittivity tunable in values and thermal stability through simply changing the composition parameter x in the doped KTN single crystals. This work provides us an effective way to design optimal dielectric materials for research and applications.