Influence of the slip composition on the aqueous processing and properties of yttria stabilized zirconia green tapes

The tape-casting process was used to produce yttria stabilized zirconia (YSZ) substrates in an aqueous system with poly(vinylalcohol) (PVA) and glycerine as binder and plasticizer, respectively. Various compositions of YSZ slips with different amounts of PVA and glycerine and consequently different solid/liquid ratios were prepared. The influence of the slip composition on the rheological properties of the slips and the drying kinetics of the cast tapes were studied. In addition, the effect of the slip composition on the properties of the resultant green tapes was investigated. PVA and glycerine did not affect the dispersion properties of the YSZ powder. The slip composition had influence only on the second stage of the drying kinetic; for a constant PVA content, the slips with higher amounts of glycerine resulted in tapes with higher drying rate. Glycerine additions enhanced the flexibility of the green tapes but also produced a decrease in the tensile strength. The increase in the PVA content increased the tensile strength but resulted in a marked decrease in the green density of the tapes. The slip compositions with 5 wt.% PVA produced green tapes with satisfactory tensile strength which had the highest green density. Since a greater amount of glycerine resulted in tapes with higher drying rate and enhanced the flexibility of the green tapes, the slip composition 5 wt.% PVA–7.1 wt.% glycerine was adequate for the production of YSZ substrates through the tape-casting process.