Porous ceramics of Y2O3-stabilized ZrO2 (YSZ) were prepared
by tape-casting methods using both pyrolyzable pore
formers and NiO followed by acid leaching. The porosity of
YSZ wafers increased in a regular manner with the mass of
graphite or polymethyl methacrylate (PMMA) to between
60% and 75% porosity. SEM indicated that the shape of the
pores in the final ceramic was related to the shape of the pore
formers, so that the pore size and microstructure of YSZ
wafers could be controlled by the choice of pore former.
Dilatometry measurements showed that measurable shrinkage
started at 1300 K, and a total shrinkage of 26% was observed,
independent of the amount or type of pore former used.
Temperature-programmed oxidation (TPO) measurements on
the green tapes demonstrated that the binders and dispersants
were combusted between 550 and 750 K, that PMMA decomposed
to methyl methacrylate between 500 and 700 K, and that
graphite combusted above 900 K. The porosity of YSZ ceramics
prepared by acid leaching of nickel from NiO–YSZ, with 50
wt% NiO, was studied as a function of NiO and YSZ particle
size. Significant changes in pore dimension were found when
NiO particle size was changed.
