Controlling colloidal processing of (K,Na)NbO3-based materials in aqueous medium

K0.5Na0.5NbO3-based materials are serious candidates to replace lead-based piezoceramics since they show excellent electrical and piezoelectric properties. The tape casting technique can be used to obtain highly textured KNN-based ceramics; however, despite industrial and environmental advantages of water-based processing, there are not reports about the control of colloidal processing conditions to obtain optimized K0.5Na0.5NbO3-based slurries in aqueous medium. This paper reports a procedure for controlling colloidal stability and rheological behavior of aqueous (K0.5Na0.5)(0.97)Li0.03Nb0.8Ta0.2O3 suspensions. Zeta potential and cationic solubility measurements as a function of pH showed that pH 8.5 is adequate for concentrated suspensions, while flow curves analysis allowed optimizing processing parameters, such as, powder content, amount of deflocculant and binder, and sonication time. Optimized colloidal suspensions were prepared and used to obtain high quality tapes. Processed ceramics from these stacked tapes show equivalent properties to those processed directly from powders, which demonstrates the effectiveness of the colloidal route reported here. (AU)