Effect of Alkali Doping on the Raman Spectra of Potassium Lithium Niobate Crystals

Raman spectra have been measured in both pure and alkali doped potassium lithium niobate (KLN) crystals. One of the A(1)(TO) Raman modes at about approximate to 640 cm(-1) measured in x(zz)x backscattering geometry is sensitive to the changes of Nb concentration. Other phonon modes at approximate to 306 cm(-1) and approximate to 350 cm(-1) corresponding to K+ and Li+ ion vibrations, respectively, have been identified by Na doping and Li-6 isotope substitution. Na+ ions substitute both for Li+ and K+ ions, while Rb+ ions incorporate only at K+ sites in KLN.