Flow properties of PLZTN aqueous suspensions for tape casting

Several aqueous suspensions of lead zirconate titanate powder doped with lanthanum and niobium (PLZTN) were prepared, tape cast and characterized by rheological measurements in steady shear flow. Experimental data were fitted by some viscous models available on literature and the model parameters compared in order to obtain information about the effects of the composition on suspension viscosity. Such approach represents a necessary step in the desirable optimization of tape casting process, which includes also the analysis by flow simulations. Five viscous models have been considered: from the classic plastic models of Bingham and Herschel-Bulkley, to the modified plastic model of Papanastasiou, up to the pseudoplastic models of Cross and Roberts-Barnes-Carew. The parameter-based comparison was carried on with the latter, resulting, with its eight parameters, the best-fit model, while for flow simulation purposes the ones with few parameters, as the Cross and Herschel-Bulkley models, resulted the more appropriate from some simple considerations.