Hydrothermal Synthesis of Nanosized <scp> Na _0.5 Bi _0.5 TiO ₃ </scp>

Abstract

The synthesis of sodium bismuth titanate Na 0.5 Bi 0.5 TiO 3 ( NBT ) was studied using the hydrothermal treatment of TiO 2 (anatase) and Bi(NO 3 ) 3 ·5H 2 O in a highly concentrated NaOH solution. The process parameters such as the alkaline conditions, the temperature, the reaction time, and the concentration, as well as the influence of the Bi/Ti ratio and microwave heating were investigated in detail. The as‐prepared NBT powders were characterized by X‐ray powder diffraction, transmission electron microscopy, energy‐dispersive spectrometry, and inductively coupled plasma atomic emission spectrometry. The results show that secondary sodium titanate phases formed along with the NBT phase in the initial stage of the reaction. Their stability was susceptible to the treatment conditions and the Bi/Ti ratio. Pure and well crystallized NBT nanoparticles were obtained after 48 h of reaction time at 200°C, 12 M NaOH , 0.1 M Bi(NO 3 ) 3 ·5H 2 O and a stoichiometric amount of TiO 2 relative to the Bi precursor. A chemical analysis of the powders showed a slight sodium deficiency and bismuth surplus with respect to their nominal composition, i.e., Na : Bi : Ti = 0.47 ± 0.02:0.53 ± 0.02:1.00 ± 0.04. The obtained NBT particles were 50–100 nm in size and exhibited great potential for further integration in composite thin films.