AC response of reduced undoped and Mg - doped LiNbO3

The temperature dependence of the AC response of undoped and Mg - doped LiNbO 3 can excellently be reproduced by assuming Maxwell-Wagner type relaxation due to an inhomogeneous distribution of insulating and conducting regions in the crystals. In the latter parts conductivity is thermally activated. The activation energy changes abruptly from 610 meV to 170 meV if [Mg] rises above ∼ 5%. This threshold concentration depends on the [Li]/[Nb] ratio. The nature of the inhomogeneities is not yet known.