PREPARATION AND PROPERTIES EVALUATION OF ZIRCONIA-BASED AL2O3 COMPOSITES ELECTROLYTES FOR SOLID OXIDE FUEL-CELL SYSTEMS .2. SINTERING BEHAVIOR AND MICROSTRUCTURAL DEVELOPMENT

The compaction behaviour of ultrafine yttria-doped zirconia powders (6 -8 nm) without and with alumina additions (0 to 20 wt %) has been stud ied. From the pore size distribution and using isothermal and nonisoth ermal techniques, the sintering behaviour of zirconia compacts in the temperature range 800-1500 degrees C was studied. It was found that al umina additions (up to 10 wt %) enhanced the zirconia compacts' densif ication process and, above that alumina content, that process was reta rded. Alumina additions did not affect the grain grown process in tetr agonal zirconia samples. However, this was strongly hindered in the fu lly stabilized zirconia ones. The results were compared with those obt ained in the same experimental conditions on a commercial zirconia pow der.