Synthesis of highly disperse tetragonal BaTiO₃ nanoparticles with core–shell by a hydrothermal method

Abstract

In order to synthesize of high-dispersion and tetragonal BaTiO 3 (BT) nanoparticle, a hydrothermal method is used in a mixture of chloride metal sources and KOH with polyvinylpyrrolidone (PVP). The properties of BT-PVPs prepared by different reaction temperature and time are investigated via XRD, FE-SEM, DLS, FT-IR, and TEM to clarify the changes of the crystal phase, dispersion, and particle structure. The reaction is finished at 230 • C for 24 h and the critical reaction condition for that the crystal phase of the obtained BT particle changed from the cubic to the tetragonal is found to be 190 • C fixed in reaction time 24 h, and 9 h. During reaction the PVP on the BT surface decomposed to different form, and the PVP plays the role of dispersant in aqueous solution. By the hydrothermal condition of 230 • C for 24 h almost monodisperse BT-PVP with sizes of 83 nm and tetragonality (c/a) of 1.0062 were synthesized. The structure of nanoparticle, core (BT)-shell (PVP) was investigated by FT-IR and direct observed by TEM and the mechanism of particle growth and dispersion was discussed.

Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

“…The size of the nanoparticles could be controlled by the Ba:Ti ratio in the precursor solution. Li et al [10] used BaCl 2 and TiCl 4 in a water-ethanol mixture with KOH as a mineralizer and obtained spherical BT nanoparticles after reactions at 230 • C for 12 h.…”

Formation Mechanism and Dispersion of Pseudo-Tetragonal BaTiO3-PVP Nanoparticles from Different Titanium Precursors: TiCl4 and TiO2

“…As introduced before, although the effect of an organic solvent such as EtOH can improve the tetragonality of the BT nanoparticles, in this study, in order to assess the effect of the Ti source, an aqueous solution was prepared without organic solvent. The synthesis parameters of the source material are 0.32 M BaCl 2 ·2H 2 O, either TiCl 4 or TiO 2 corresponding to a 0.2 M Ti source, 100 g/L PVP, and 2.3 M KOH, under the reaction conditions of 230 °C for 24 h, which were optimized in previous research [ 20 ]. Figure 1 a shows the change in the mean particle size (PS) of BT-PVP that was prepared by substituting the raw material TiCl 4 by TiO 2 , and the tetragonality, the c/a ratio of the pseudo-tetragonal structure.…”

“…In addition, it can be seen that the particles are covered with gel in Figure 2 a, but not in Figure 2 b, and the amount of dispersant adsorbed on the BT surface is 4.09 and 2.28 wt % respectively, measured by thermogravimetric analysis (TG), indicating that the 5 h reaction time is still too short to decompose PVP completely when TiCl 4 is used as the source. In our previous study [ 20 ], BT-PVP prepared by a hydrothermal process demonstrated high dispersion because PVP completely decomposed as the reaction time became longer, and the dispersion worsened as the reaction time shortened because the PVP was incompletely decomposed as measured by Fourier transform infrared spectroscopy (FT-IR, FT/IR-610, JASCO Corp., Tokyo, Japan). The dispersibility of the particles prepared by both sources was less than satisfactory, but as the reaction time was extended to 24 h, good dispersion was obtained.…”

“…We previously reported that the PVP decomposes with increasing reaction temperature and time in the hydrothermal process [ 20 ]. The highly dispersed state of BT-PVP is maintained by the decomposed PVP absorbed on the BT surface via electrostatic repulsion.…”

Facile Low Temperature Hydrothermal Synthesis of BaTiO₃ Nanoparticles Studied by <em>In Situ</em> X-ray Diffraction

“…The size of the nanoparticles could be controlled by changing the Ba:Ti ratio in the precursor solution. Li et al [10] used BaCl2 and TiCl4 in a water-ethanol mixture, with KOH as a mineralizer and obtained spherical BT nanoparticles after reactions at 230 °C for 12 h.…”