Phase Evolution of BaTiO3 Nanoparticles: An Identification of BaTi2O5 Intermediate Phase in Calcined Stearic Acid Gel

Thermal decomposition of stearic acid gel was employed to study the phase evolution of BaTiO3 nanoparticles by thermal gravimetric analysis, X-ray diffraction, Fourier transform infrared, and UV−vis diffuse reflectance spectra. The calcined process of stearic acid gel consisted of a series of oxidation and combustion reactions in air, accompanied by strong exothermal effects. When the stearic acid gel was calcined in air, some organic-Ba was easily transformed into BaCO3 crystallites even at low calcined temperatures, while the organic-Ti, combining with the rest of the organic-Ba could only form the intermediate phase BaTi2O5 instead of TiO2 crystallites, which reacted with BaCO3 to form BaTiO3 nanoparticles. The intermediate phase BaTi2O5 existed very shortly in the calcined process and was successfully identified in the current work.