Part of the book: Advances in Ceramics
Part of the book: Advances in Ceramics
Barium zirconate has emerged as the leading candidate material for fabricating dense ceramic membranes for hydrogen separation. B-sites in the ABO3 perovskite are acceptor-doped with a +3 cation – most commonly yttrium – charge-compensated by the formation of oxygen ion vacancies in the lattice. A minor fraction of B-sites can be filled with cerium to give BaZr0.9-xCexY0.1O3-d, x ≤ 0.2. Upon hydration at elevated temperatures, weakly-bound protons are formed in the lattice. This produces a cubic perovskite ceramic proton conductor useful in diverse applications, such as protonic ceramic fuel cells, electrolysers, and catalytic membrane reactors operating at temperatures between 600 and 800 °C. A necessary requirement for fabricating thin ceramic membranes for proton diffusion is to maximize grain size while eliminating percolating porosity. However, high-density, large-grained barium zirconate is a very difficult material to prepare by traditional powder sintering methods. This chapter describes a new methodology for making protonic ceramic membranes with large grains and virtually no residual porosity. This discovery has the potential to have a profound impact on energy conversion efficiency of the various membrane devices envisioned for the coming hydrogen energy economy.
Part of the book: Perovskite Materials