Spark-plasma-sintered barium zirconate based proton conductors for solid oxide fuel cell and hydrogen separation applications

Proton conducting ceramics exhibit high levels of bulk proton conductivity at intermediate temperatures (500-700 degrees C). However, this material class has not been widely utilized in energy conversion and storage applications due to the blocking behavior of the grain boundary proton conduction. A better understanding of proton conduction in these materials requires a systematic study of the sintering conditions that determine microstructure and ultimately the electrical properties. In this work, spark plasma sintering with high heating rates was employed to prepare a state-of-the-art BaZr0.9Y0.1O3-delta (BZY) proton conductor for studies focused on the behavior of proton conduction at the grain boundary interfaces. The ceramics prepared by the SPS method resulted in an ultra-fine grain size of approximately 200 nm. The large grain boundary interfacial area was used as a tool to investigate the interfacial conduction in these materials systems. Samples displayed a lowered grain boundary conductivity and a higher activation energy compared with the literature results on conventionally prepared materials. The lower bulk conductivity is interpreted with reference to polymorphs of BZY sintered at different temperatures. The combined effect led to a lower total conductivity of the SPS densified BZY ceramics. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.