WIDE FREQUENCY-RANGE DISPERSION AND RELAXATIONS IN CERAMICS OF THE K6LI4TA10O30-PB5TA10O30 SYSTEM

Dielectric and impedance measurements were performed on ceramics with composition Pb-5x K6(1-x)Li4(1-x)Ta10O30, in wide frequency and temper ature ranges, 10(1) to 10(9) Hz and 100 to 650 K, respectively. At low frequency and low temperature, a relaxer behavior is found for compos itions corresponding to x > 0.70. Moreover, two other relaxations are observed: an ionic conduction relaxation at low frequency and high tem perature and a network relaxation at high frequency and low temperatur e. The former is explained on the basis of the motion of Lif cations i n sites of coordination number 9 and the latter on the basis of correl ation chains.