Effect of solvents on the morphology and structure of barium titanate synthesized by a one-step hydrothermal method

Tetragonal barium titanate was synthesized from barium hydroxide octahydrate and titanium tetrachloride through a simple one-step hydrothermal method. The effect of different solvents on the crystal structure and morphology of barium titanate nanoparticles during the hydrothermal process was investigated. Except for ethylene glycol/water solvent, impurity-free barium titanate was synthesized in pure water, methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents. Compared with other alcohols, ethanol promotes the formation of a tetragonal structure. In addition, characterization studies confirm that particles synthesized in methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents are smaller in size than those synthesized in pure water. In the case of alcohol-containing solvents, the particle size decreases in the order of isopropanol, ethanol, and methanol. Among all the media used in this study, ethanol/water is considered the optimum reaction media for barium titanate with high tetragonality (defined as the ratio of two lattice parameters c and a, c/a = 1.0088) and small average particle size (82 nm), which indicates its great application potential in multilayer ceramic capacitors.