IMPEDANCE-SPECTROSCOPY ANALYSIS OF A LITAO3-TYPE SINGLE-CRYSTAL

Low-frequency dielectric dispersion phenomena in a LiTaO3-type single crystal have been analyzed by impedance spectroscopy in directions par allel and perpendicular to the polar c-axis (rhombohedral system)/ An empirical expression has been deduced for the complex permittivity eps ilon()(omega), epsilon(*)(omega) = epsilon(infinity) + epsilon(s) - e psilon(infinity)/1 + (i omega/omega/omega(1))(m) + sigma 0/epsilon(0) omega [1 + (i omega/omega(2))(n)], where the (omega(1), m) and (omega( 2), n) couples characterize respectively the lattice and the charge ca rrier responses. This relation may be considered as a generalization o f the Cole-Cole dielectric expression [J. Chem, Phys. 9, 341 (1941)]. Excellent agreement has been obtained in a wide frequency domain (1-10 (6) Hz) between the measured and calculated permittivities in the 500- 650 degrees C temperature range (T-c = 600 degrees C), The temperature dependence of various dielectrical parameters has been determined and discussed. The relaxations are correlated to Li atom motions. (C) 199 5 Academic Press, Inc.