Comparative two- and four-probe impedance measurements on BICUVOX.10

In two-probe impedance measurements the interfacial impedance between metal electrode and ionic conductor contributes to the measured impedance. Therefore a calculation procedure which separates the bulk from the interfacial impedance must be applied. The separation procedure can be avoided by measuring the bulk conductivity in the four-probe arrangement. The impedance of polycrystalline samples and single crystals of the oxygen ion conductor BICUVOX.10 was measured in the a.c. two- and four-probe configuration. The frequency range was 0.1 to 1 x 10(6) Hz in the case of two-probe measurements and 0.1 to 1 X 10(5) Hz in the case of four-probe measurements. For single crystals, impedance spectra were taken in the direction parallel to the oxygen-conducting layers. The results of bulk conductivity obtained by four- and two-probe measurements were in agreement for polycrystalline samples and for single crystals. The origin of inductive loops visible for single crystals in the impedance spectra taken by the four-probe method is explained in a qualitative fashion as an interfacial effect at the voltage electrodes. (C) 1999 Elsevier Science B.V. All rights reserved.