The AC conductivity and dielectric constant of lithium niobate single crystals

Abstract

The AC conductivity sigma ( omega ) and dielectric constant epsilon ' of lithium niobate single crystals have been measured along the ferroelectric c-axis in the temperature range 77-700K and in the frequency region 0.1-100 kHz. At low temperatures, below 400K, the AC conductivity can be expressed as sigma ( omega )=A omega s, where the slope s is close to unity and decreases with increasing temperature. The dielectric constant in this temperature region shows a weak frequency and temperature dependence. At higher temperatures, above 400K, the AC conductivity shows a strong temperature dependence and weak frequency dependence. The dielectric constant in this region also shows a strong frequency dispersion. The mechanism of conduction in low and high temperature regions is discussed in the light of existing theoretical models.