Optical and electrical studies on trivalent-ion (Cr, Fe)-doped potassium titanyl phosphate single crystals

In this paper we report the effect of trivalent ion (Cr and Fe) doping on the ionic conductivity and dielectric properties of self-flux-grown Potassium Titanyl Phosphate (KTiOPO4; KTP) single crystals. Their electrical properties revealed that Cr- and Fe-ion-doped KTP single crystals exhibit a lower ionic conductivity (1-2 orders of magnitude) than that of pure crystal. However, the frequency and temperature dispersion of the ionic conductivity and dielectric constant of Cr-and Fe-ion-doped KTP crystals are almost similar to pure KTP crystals. The measured activation energy indicates the existence of superionic conduction behavior. The incorporation of trivalent ions shifts the optical absorption edge in the UV-VIS spectrum towards the long-wavelength region and increases the optical absorption coefficient of KTP crystals. Vickers microhardness results showed that trivalent ion doping decreases the mechanical strength of pure KTP crystals.