Role of urea addition in the preparation of tetragonal BaTiO3 nanoparticles using flame-assisted spray pyrolysis

In this study, flame-assisted spray pyrolysis (FASP) was used to produce BaTiO3 nanoparticles with relatively high tetragonality and controlled sizes from 23 to 33 nm in a one-step process. The addition of urea into the precursor is the key factor for the formation of tetragonal BaTiO3 nanoparticles; the lack of urea addition led to the formation of submicrometer BaTiO3. The formation of BaTiO3 nanoparticles was suggested from the disintegration of submicrometer particles due to the decomposition of urea presented in the interconnection of their primary particles. Also, combustion of the decomposed gases of urea produced additional heat, which improved the tetragonality of the BaTiO3 nanoparticles. Tetragonality was enhanced from 1.0051 to 1.0071 by increasing the urea addition to as high as 4 M. The results of the present study show that addition of urea to the precursor is an effective strategy for the direct production of tetragonal BaTiO3 nanoparticles using the FASP method.