Dielectric properties and optical absorption of KTaO₃single crystals and KTaO₃.NaTaO mixed crystals

Abstract

The dielectric constant K, loss tan delta and conductivity sigma of single crystals of pure KTaO3 and KTaO3. NaTaO3 mixed crystals (with 2, 12 and 35% Na) were determined as a function of frequency from 102 to 107 Hz and in the temperature range 30-350 degrees C. The dielectric constant at 30 degrees C decreases with frequency in all these samples. The tan delta values are below detection level at room temperature. The larger values of K at lower frequencies are attributed to crystal defects. The dielectric constant of all these samples decreases considerably with temperature at all frequencies but at 102 Hz, and from around 190 degrees C, it starts increasing with temperature This inversion temperature is found to increase with frequency but decrease with Na content. Dielectric loss is found to increase with temperature but decrease with frequency. Lg sigma plotted against 1/T for these samples shows that the intrinsic conductivity region is not reached even at 350 degrees C.