Infrared OH? Absorption Bands in Potassium Lithium Niobate Single Crystals

Abstract

Subject classification: 61.72. Ww; 78.30.Hv; S10.15 The existence of protons (H þ ) was characterized by infrared absorption spectroscopy in potassium lithium niobate single crystals with a lower than 1.5 Li content. The as-grown crystals showed a broad OH -stretching vibration near 3500 cm --1 and contained about 5.5 Â 10 18 cm --3 protons. Especially, the concentration of the protons increased about one order of the magnitude after heat treatment in a humid atmosphere. From the measurements of the polarization dependence of the OH -absorption bands in this crystal, we can expect that the OH -ions vibrate along the c-axis and O-O edges of an oxygen octahedron. It shows a different aspect in comparison with LiNbO 3 single crystals due to the different structure and the cation environment.