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

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 20–100K 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 100–200K is likely due to the reorientation of the dipolar structure Fe3+-Oi 2- 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. [ABSTRACT FROM AUTHOR]