Tritium conductivity and isotope effect in proton-conducting perovskites

The tritium ion conductivities of SrZr0.9Yb0.1O2.95 and BaCe0.9Yb0.1O2.95 h ave been measured by ac impedance analysis. The high tritium conductivity o f these perovskites could potentially lead to their application as an elect rochemical membrane for the recovery of tritium from tritiated gas streams. The conductivities of these perovskites, along with SrCe0.95Yb0.05O2.975 w ere also measured in hydrogen- and deuterium-containing atmospheres to illu strate the isotope effect. For the strontium zirconate and barium cerate sa mples, the impedance plot consists of two clearly resolved arcs, a bulk and a grain boundary are, in the temperature range 50-350 degrees C. However, for the strontium cerate sample, the clear resolution of the bulk conductiv ity was not possible and only the total conductivity was measurable. Thus, the isotope effect was clearly established only for the strontium zirconate and barium cerate samples. The decrease in bulk conductivity with increasi ng isotope mass was found to be a result of an increase in the activation e nergy for conduction accompanied by a decrease in the pre-exponential facto r. Since the concentration of the mobile species (H+, D+, or T+) should rem ain relatively constant at T < 350 degrees C, this increase in activation e nergy is directly attributable to the increased activation energy for the i sotope mobility. (C) 1999 The Electrochemical Society. All rights reserved.