AVS 49th International Symposium
    Dielectrics Wednesday Sessions
       Session DI+EL-WeP

Paper DI+EL-WeP4
Influence of Impurities on Attenuation of Acoustic Waves in LiNbO@sub3@ Crystals

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Poster Session
Presenter: M.M. Akhmedjanova, Samarkand State University, Uzbekistan
Authors: F.R. Akhmedzhanov, Samarkand State University, Uzbekistan
M.M. Akhmedjanova, Samarkand State University, Uzbekistan
Correspondent: Click to Email
In present work the attenuation of longitudinal and transverse acoustic waves in pure LiNbO3 and Mg, Zn, Cu and Cr doped LiNbO3 crystals have been investigated in detail. The weight concentration of above-mentioned impurities in investigated samples was consisted 0.01-0.02 percents. The measurements of attenuation coefficient carried out by Bragg light scattering method at the temperatures 295 K and 480 K. Piezoelectric transducers of Lithium Niobate of appropriate cuts are used in order to excite the longitudinal and the transverse acoustic waves with the frequencies of 0.3-1.8 GHz. The values of attenuation coefficients were determined from the measurements of the dependence of the scattered light intensity from the distance to the piezotransducer along the direction of the acoustic wave propagation. The obtained values of the scattered light intensities have been used to calculate the quantity and frequency dependence of the attenuation coefficient of the acoustic wave. The velocities of all the investigated waves were with sufficient accuracy determined from the experimental data simultaneously. The results of measurements have shown that in crystals with impurities are observed the changes in the attenuation of acoustic waves. Also have shown that the impurity of Cr causes increase of the attenuation of longitudinal waves on 20-50% but at the same time decreases the attenuation of transverse waves almost in two times. At the same time impurities of Cu, Zn, Mg reduce the decrease of attenuation the longitudinal waves in 1,5-2 times and insignificantly increase of the attenuation of the transverse waves. The obtained results are interpreted in framework of various mechanisms of attenuation including the electron-phonon, Akhiezer and Landau-Khalatnikov mechanisms. The influence of dielectric losses on the attenuation of piezoactive acoustic waves in LiNbO3 crystals is also discussed.