Ac conductivity for Eu2Zr2O7 and La 2Ce2O7 with pyrochlore-type composition

Abstract

Ac conductivity (σac) obtained from admittance of Eu 2Zr2O7 and La2Ce2O 7, which have pyrochlore- and fluorite-type structure, respectively, was measured as a function of frequency in the range between 5 Hz and 13 MHz and in the temperature range between 573 and 1073 K. The frequency dependence of the σac of these oxideion conductors showed a remarkably different behavior from that of the cation ones. By comparison of the σac with other conductivity data obtained by dc four-probe and impedance spectroscopic methods, it was found that the σac in the frequency range below 105 Hz was strongly influenced by space charge polarization at grain boundary and that the σac obtained from high frequency plateau agreed with bulk conductivity, σib, from impedance spectra and dc conductivity, σdc.