Low-temperature synthesis of bismuth titanate by modified citrate amorphous method

Bismuth titanate is a lead-free piezoelectric ceramic with outstanding properties that strictly depend on the composition and microstructure. However, bismuth-based materials are difficult to synthesize due to bismuth volatilisation that causes secondary phases and stoichiometry deviations. In this work, we propose a low-temperature chemical route, i.e. a modified amorphous citrate method, that allows a reduction of thermal treatment temperature, when compared with solid-state or other chemical routes, to obtain single-phase bismuth titanate samples. Single-phase powders with particle size under 300 nm are produced by calcination at 700 °C, and prepared into homogeneous dense pellets (density above 95%), with only isolated pores. The pellets show two distinctive features in the electrical behaviours directly associated with their mica-like microstructure: planar oriented boundaries are responsible for oxygen conduction, while the bulk is dominated by electronic conductivity. The samples show a high dielectric constant, around 200 at room temperature, while maintaining a low loss factor. The pellets also achieved a maximum polarisation of 5.85 μC/cm2 and an inverse piezoelectric coefficient of 7.4 pm/V. The dielectric and piezoelectric properties obtained are comparable or superior to the state-of-the-art.