Alumina and zirconia were dispersed individually in aqueous media using Darvan C as the dispersant and at optimised pH condition. Based on sedimentation, rheology, yield stress, electrodeposition and zeta potential measurements, 2 wt-% of the dispersant and a pH of 10 . 5 were found to be the optimum condition for the codispersion of alumina and zirconia. Aqueous tape casting slurries with a solid loading of 32 wt-% were prepared under the optimised conditions of dispersion. Alumina-zirconia (50 : 50) composite tapes of 40 mm thickness and 56% green density were obtained.
The present study focuses on critical factors limiting single-phase formation of Ba 2 Ti 9 O 20 (2 : 9). Apart from 2 : 9, other polytitanates that are richer in Ti or Ba could also be prepared as single-phase material without any stabilizing agent through chemical co-precipitation. 2 : 9 is found to be a stoichiometric compound and even 0⋅5% excess Ti or Ba leads to multiphase formation. Single-phase 2 : 9 could be achieved even through solid-state route without the addition of stabilizing agents using high purity raw materials. The present results do not agree with existing hypotheses viz. diffusion, high surface and nucleation energy, potential barrier, nonstoichiometry etc as critical factors limiting formation of 2 : 9 as single-phase material.
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