Synthesis, chemical stability and proton conductivity of the perovksites Ba(Ce,Zr)_1−x Sc_x O_3 − δ

Rare-earth-doped BaCeO3 and BaZrO3 electrolytes with perovskite structure have been studied extensively in developing intermediate temperature SOFC. Traditional solid state sintering has been used to prepare the perovskite type proton conductors Ba(Ce,Zr)](1-x)ScxO3-delta (x= 0.1, 0.2). Rietveld refinement of the XRD data shows the materials as cubic in the space group Pm-3m. The unit cell parameter a decreases with Sc concentration. Thermogravimetric analysis (TGA) traces obtained for dehydrated samples on heating in a 3% H2O/5% H-2/Ar atmosphere show that, on heating, initially the sample weight remains constant up to 400 degrees C and then decreases. TGA in pure CO2 shows that Sc doping increases the chemical stability. AC impedance measurements under wet 5% H-2/Ar show that these materials are good conductors and stable under H-2 atmosphere. It also shows that bulk and grain boundary resistances decrease with Sc doping. The total conductivity increases from 2.58 x 10(-4) Scm(-1) to 1.06 x 10(-3) Scm(-1) for x=0.1 and 0.2 respectively at 600 degrees C. (C) 2007 Elsevier B.V. All rights reserved.