Oxygen ionic and electronic conductivity of La-doped BIMEVOX

Doping by either lanthanum or nickel has been found to result in decreasing ionic conductivity and thermal expansion of the Bi2-cLaxV1-y-zCuyNizO5.5-delta (s = 0.10-0.20; y = 0-0.10; z = 0-0.20) ceramics. The infrared absorption spectroscopy data on Bi2-xLaxV1-y-zCuyNizO5.5-delta have been shown to correlate with the conductivity and crystal structure of the oxides. The thermal expansion coefficients of the ceramics are (13.5-15.5)x10(-6) K-1 at temperatures of 300-570 K and (14.8-18.6) X 10(-6) K-1 at 580-1050 K. Ion transference numbers of Bi2-xLaxV0.90Cu0.10O5.5-,delta (x = 0.10-0.20) have been determined by Faradaic efficiency measurements at 720-800 K to vary in the range from 0.65 to 0.95. Doping by lanthanum results in increasing electronic conductivity. A new experimental arrangement to study Faradaic efficiency of oxygen ionic conductors has been suggested and verified. (C) 1998 Elsevier Science B.V. All rights reserved.