Influencing Factor Investigation on Dynamic Hydrothermal Growth of Gapped Hollow BaTiO3 Nanospheres

Gapped hollow BaTiO3 nanospheres with an apparent diameter of 93 ± 19 nm (shell thickness of 10-20 nm) were synthesized via a dynamic hydrothermal process using TiO2 sols and Ba(2+) ions as the Ti and Ba sources in alkaline aqueous solutions. The phases and morphologies of the BaTiO3 samples were characterized by X-ray diffraction (XRD), SEM, TEM, and Raman spectra. The effects of the hydrothermal temperatures and durations, NaOH concentrations, and Ba/Ti ratios on the formation of gapped hollow BaTiO3 nanospheres were systematically investigated. The optimum conditions for forming gapped hollow BaTiO3 nanospheres are hydrothermal treatment at 180 °C for 10-20 h under a continuous magnetic stirring with NaOH concentrations of about 1 mol/L and molar Ba/Ti ratios of 1.2-1.5. The formation mechanism of the gapped hollow BaTiO3 nanospheres is understood as the combination of the orientated attachment and reversed crystal growth.