Study of the Transport Properties of the Mixed Ionic Electronic Conductor Ce_(1-x)Tb_xO_(2-δ) + Co (x = 0.1, 0.2) and Evaluation As Oxygen-Transport Membrane

摘要

Tb-doped ceria materials have been synthesized by the coprecipitation method. Cobalt oxide (2 mol %) has been added in order to improve the sinterability and conductivity. XRD measurements suggest that a part of the cobalt is incorporated in the ceria lattice. Ce_(1-x)Tb_xO_(2-δ) materials showed predominantly ionic conductivity, but the mixed ionic electronic conductivity can be tuned by modifying Tb and Co doping level and temperature range. The ambipolar conductivity was determined by galvanic method coupled with gas permeation and these results support the applicability of these materials as oxygen transport membranes at high temperature. Ce_(1-x)Tb_xO_(2-δ) +Co membranes are CO2 stable and yielded oxygen fluxes that can compete with reported perovskite materials. Oxygen diffusion and surface exchange coefficients in the range 1 x 10~(-5) to 1 x 10~(-4) cm~2/s and 1 x 10~(-4) to 1 X 10~(-3) cm/s from 773 to 1023 K have been obtained by conductivity relaxation.