Low temperature dc electrical conduction in reduced lithium niobate single crystals

The direct current (dc) electrical conductivity of unreduced and reduced lithium niobate (LiNbO3) single crystals has been measured at room temperature (similar to 300 K). The dc conductivity and activation energy show strong dependence on the degree of oxygen reduction in LiNbO3 single crystals. The dc conductivity exhibits a peak as a function of increasing degree of oxygen reduction. These results have been analysed assuming small polaron hopping conduction between Nb4+ and Nb5+ ion sites. The temperature dependence of dc conductivity of reduced LiNbO3 single crystal, exhibiting the highest dc conductivity, has been examined in the temperature range 77-373 K. The observed dc conductivity data has been analyzed and explained in terms of Mott's variable range hopping (VRH) conduction model involving a single phonon hopping process. (C) 2012 Elsevier Ltd. All rights reserved.