Analysis of the Nature of Electrical Conductivity in Nominally Undoped LiNbO3 Crystals

The temperature dependence of electrical conductivity and admittance of two nominally undoped lithium niobate crystals of congruent composition has been investigated in the temperature range of 293-450 K and simulated in the range of 350-700 K. It is shown that the ion conductivity at T < 450 K is mainly determined by OH- groups; however, some other mechanisms may manifest themselves at higher temperatures; a likely one is diffusion of oxygen vacancies, which leads to an increase in the averaged conductivity activation energy.