Nickel coarsening in annealed Ni/8YSZ anode substrates for solid oxide fuel cells - In memoriam to Professor H. Tagawa

In order to study the nickel coarsening in porous Ni/8YSZ anode cermets of solid oxide fuel cells (SOFC), a series of exposure tests was carried out w ith anode substrates used in SOFC development at the Research Centre Julich . The changes in electrical conductivity as well as in the microstructure o f the material were investigated. The microstructure of the cermets was cha racterized by digital on-line image analysis and microstructural parameters were determined for the metallic and the ceramic phase as well as for poro sity. A decrease of 33% of the initial electrical conductivity was measured after exposing the cermet in Ar/4% H-2/3% H2O at 1000 degrees C for 4000 h , which is linked to the agglomeration of the metallic particles of this ma terial. The durability of anode cermets for operations of up to 40 000 h wa s estimated on the basis of the measured grain coarsening and the decrease of conductivity. The microstructural parameters - like volume fraction, par ticle and pore size - were used to model the electrical conductivity by the oretical microstructure-property relationships. (C) 2000 Elsevier Science B .V. All rights reserved.