Synthesis and electrical conductivity of gd-doped bapro3 powders

Abstract

BaPrl-xGdxO3-d (GBP) was first discovered and proposed as potential proton conducting electrolyte in IT-SOFC in 1998. Its conductivity was reported to be the highest among all protonic conductors reported to date, even higher than doped BaCeO3. In the present work, GBP has been synthesized by using the acrylamide combustion method, which renders a final material with lower particle size, lower temperature sintering and better homogeneity than those obtained by the classical solid state method. Phase purity was achieved after a single thermal treatment of the precursor powder at 1000 °C during 5 hours. The material was characterized by X-ray diffraction, SEM, BET and thermogravimetric and thermodifferential analysis. SEM revealed the nanometric particles (∼ 150 nm) and BET confirmed partial sintering among them (2.85 m2/g; ∼320 nm). Sintering of bulk material is easily achieved using conventional uniaxial pressing. Stability tests under 5% H2/Ar and pure O2 are presented. The crystal structure remains unaltered under O2, but decomposition under H2 atmosphere occurs beyond 420°C. AC impedance spectroscopy has been also performed on dense samples in 5% H2/Ar and pure O2, both dry and wet, well below 420°C, the decomposition temperature in reducing conditions. It was noted that in all these measurements, the total conductivity is dominated by hole conduction. The different behaviour of the conductivity of the material under different conditions is discussed.</p