Abstract: In order to develop an efficient gelcasting technique used for lead free piezoceramics, aqueous gelcasting was applied to prepare 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃(BNBT6) ceramic and its effects on the ceramic microstructure and piezoelectric performance were intensively investigated as well. PMAA-NH4 was used as the dispersant in the process. When the suspension contained 0.5wt% PMAA-NH4 and pH value was adjusted at around 9.2, the BNBT6 suspension was stable with low viscosity (<1Pa·s) and high solid loading (50vol%). The dipping pretreatment was also conducted for pre-drying gelled parts. In the process, the gelled parts were immersed in 10wt% ammonium persulphate solution for 8--10h. After the dipping pretreatment, desiccation and dehydration of the gelled parts without defects became easily controlled. SEM micrographs show that the BNBT6 ceramic prepared by the gelcasting route exhibits homogeneous microstructure and high density. The optimal piezoelectric and dielectric properties are obtained, namely d₃₃=132pC/N; ε_r=1319; tgδ=0.019.

Key words: lead-free piezoceramic, gelcasting, dipping pretreatment, piezoelectric property