Facile preparation of uniform barium titanate (BaTiO3) multipods with high permittivity: impedance and temperature dependent dielectric behavior

Abstract

Perovskite barium titanate (BaTiO₃) multipods were prepared via high temperature solid state reaction. The crystal structure and morphology of BaTiO₃ particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and scanning probe microscopy (SPM). The XRD analysis of the crystal structure revealed that a single-phase compound was formed having tetragonal crystal structure. Calorimetric study (DSC) over room to high temperature was used to find the energy involved in different steps of synthesis especially during the initiation and the termination process for the formation of BaTiO₃. These multipods have high average aspect ratio (∼10, where average diameter ∼300 nm and average length ∼3 μm) as seen from FESEM. UV-Vis spectroscopy reveals that the prepared material is UV active. The bulk and surface chemical composition of these BaTiO₃ particles as investigated by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra reveals that in the prepared BaTiO₃, the titanium ions exist in two different oxidation states, namely Ti³⁺ and Ti⁴⁺. The BaTiO₃ multipod exhibits high permittivity with relatively low dielectric loss. From impedance analysis of the material, the dual resistivity characteristics, one for grain and the other for grain-boundary can be distinguished. An equivalent circuit has been proposed through analysis of the complex impedance plot (Nyquist plot) for BaTiO₃ multipods. This material has perfect capacitative nature as seen from the Bode plot, and can be used for charge storage devices and other electronic applications. From temperature dependent dielectric analysis, the Curie temperature of BaTiO₃ multipods is found to be ∼85 °C.