Aqueous Tape Casting Using Organic Binder: A Case Study with YSZ

Abstract

Aqueous tape casting of yttria stabilized zirconia (YSZ) having very wide particle size range was investigated using biopolymer, gelatin as binder and glycerol as plasticizer. Best dispersion of YSZ powder was obtained by using an anionic polyelectrolyte DARVAN 821A at pH 7.5. Gelling properties of gelatin, plasticized with water and glycerol have been studied by dynamic shear measurements. Decreasing concentration of gelatin significantly decreases the gelling temperature of it. With the addition of optimum amount of binder and plasticizer, it has been possible to prepare stable YSZ suspension of 45-50 wt% solid loading that exhibited the desired shear-thinning behavior. Green tapes with good flexibility (strain to failure: 12%-24%) and strength (2-3 MPa) with total organics content of 10-14 wt % were obtained. After removal of organics, the tapes were sintered at 1550 degrees C for 3 h. The sintered density of the tapes thus obtained was about 99% of the theoretical density. The grain size of the sintered tape was fairly large (10-20 mu m); but the surface of the sintered tape (thickness: 100 mu m) did not show any visible porosity.