ANALYTICAL DISTRIBUTIONS OF RELAXATION-TIMES FOR THE DESCRIPTION OF ELECTRICAL-CONDUCTIVITY RELAXATION IN IONIC CONDUCTORS

Electrical conductivity relaxation was measured in three different ion ic conductors (yttria-stabilized zirconia, Li0.5La0.5TiO3 and Li0.5Na0 .5La(CrO4)(2)), using the admittance spectroscopy technique. A study o f the frequency dependence of the dielectric modulus is presented, whi ch shows that the Havriliak-Negami dielectric functions describe the r elaxation process accurately This allows the use of an analytical dist ribution of relaxation times to determine the time decay function from admittance data in the frequency domain. Electrical conductivity rela xation of the measured ionic conductors has been analysed using this m ethod showing strong non-Debye frequency behaviour and 'stretched'-exp onential Kohlrausch-Williams-Watts time decay functions. The results o btained are interpreted in terms of cooperative effects or correlation among ions. Activation energies for long- and short-range ion motion are deduced.