RAMAN AND INFRARED REFLECTIVITY SPECTRA OF POTASSIUM LITHIUM-NIOBATE SINGLE-CRYSTALS

The tetragonal tungsten bronze (TB) type potassium lithium niobate (KL N) single crystals were grown using the conventional pulling method. T he molecular formula can be written as K2.96Li1.97Nb5.07O15 based on t he crystal atomic absorption spectra. The lattice constants are a=1.25 75+/-0.0001 nm and c=0.3997 +/-0.0001 nm. The Curie temperature is 430 +/-3 degrees C, Homogeneous and crackfree samples of about 7 x 7 x 5 m m(3) were used to study the lattice vibration spectra using Raman and infrared reflectivity spectroscopy. Compared with the lattice vibratio n spectra of other TB type crystals, we see that the influence of the Li ions in the C sites in the KLN on the characteristic Raman and infr ared reflectivity spectra of the Nb-O octahedral ions is sulking. Spec ially, the symmetric bend vibration mode nu(5) was split into three Ra man lines, and the antisymmetric stretch vibration mode nu(3) and the antisymmetric bend vibration mode nu(4) were all broadened greatly.