A study was made of the effect of correlated ionic motions upon conductivity relaxation in monocrystalline samples of yttria-stabilized material. Complex admittance data for the radio-frequency range revealed the power-law dependences of the real part of the conductivity at high frequencies. An analysis of the frequency dependence of the electric modulus was performed in order to obtain exponential time decay functions from an analytical distribution of relaxation times. The correlation times, and the parameters which characterized relaxation in the time and frequency domains, were compared so as to demonstrate the equivalence of time and frequency representations. A common origin for the alternating-current and direct-current processes was considered in terms of the frequency dependence of the complex conductivity. From a macroscopic activation energy for ion motion (1.16eV), and a decay-factor exponent of 0.43, a single-ion microscopic activation energy of 0.5eV was deduced according to the Ngai coupling model. The microscopic activation energy was related to the association energy of O vacancies.

C.León, M.L.Lucía, J.Santamaría: Physical Review B, 1997, 55[2], 882-7