By: John Kilner - Department of Materials, Imperial College London
When: April, 26 - 11AM
Where: sala de seminarios, 182 - ICMM-CSIC
Abstract: The development of materials for solid oxide electrochemical devices has been a topic of interest for a number of decades. In particular, the use of porous ceramic Mixed Ionic Electronic Conductors (MIECs) for use as electrodes has been pursued because of their excellent performance as air electrodes in solid oxide cells. A typical example is the mixed conducting perovskite oxide La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF6428) , where the oxygen diffusivity approaches 10-8cm2s-1 at 750C.
As technology has progressed, there has been a desire to lower the temperature of operation. As the operation temperatures reduce the transport of oxygen ions in the lattice drops to levels where it is no longer enough to give satisfactory performance as an electrode. This has led to the concept that oxygen transport along interfaces, both homogenous and heterogeneous, can be promoted to give a suitable net oxygen transport. For MIEC materials, gaining an understanding of the grain boundary transport of oxygen is key to developing ideas of grain boundary engineering to enhance performance at the lower temperatures. This contribution will cover some of the recent progress that has been made in understanding the grain boundary chemistry of these complex oxide materials and the effect that this can have on the transport of oxygen.
In addition the role of processing and thermal history will be explored for all complex ionic conducting materials, both cation conductors (Li, Na) and anion conductors (O,F). These are cases where ions on one sublattice has a mobility many orders of magnitude higher than that of the much more immobile “framework”. This enormous difference has consequences for the distribution of the non-mobile ions at interfaces such as surfaces and grain boundaries.
