Ceramic conductors for electrochemical cell applications: new perspectivesin materials and synthesis

A great number of compounds with electronic and ionic conductivity and new synthesis routes are being explored for electrochemical applications. In th is work, selected examples are described. (a) CaO-TiO2-Fe2O3 materials prep ared by combustion synthesis are low cost products with interesting mixed c onduction, the electrical behavior of which indicates the existence of a tr ansition, where the grain interior electrical contribution is the dominant effect from 7% mol iron content. (b) Mixed electronic-ionic conducting SmCo O3 perovskites with dispersed Pt particles were prepared by combustion synt hesis. The as-prepared powders showed very small metallic Pt particles and exhibited acceptable catalytic performance in methanol oxidation. (c) Mater ials belonging to the Ti1-xRuxO2 system, 0 less than or equal tox less than or equal to1 (mol), were synthesized by a polymeric sol-gel route. Two typ es of electrical behavior were detected in sintered materials of this syste m: semiconductor and metallic. A wide semiconductor/metal transition was ob served. The metal/electrical percolation could be located at a composition of x = 0.26. (d) On the other hand, amorphous nanopore materials with proto nic conduction obtained by appropriate synthesis can be used as electrolyte s in PEMFCs. SiO2 nanopore ceramic membranes were prepared using a colloida l sol-gel technique. The chips were mesoporous with an average pore size of 3.5 nm. (C) 2000 Elsevier Science BSI. All rights reserved.