Structural, optical and electrical properties of SnO2 doped TiO2 synthesized by the Sol–Gel method

Abstract

SnO2 doped TiO2 materials have received considerable attention due to their high dielectric permittivity (on the order of 10,000) and low loss factor (< 0.1) over a broad temperature/frequency range. In this work, a SnO2–TiO2 nanocomposite was successfully synthesized by a single solvent process. The synthesized samples were characterized by X-ray diffraction, high resolution scanning electron microscopy, UV–Vis spectroscopy, photoluminescence and impedance analysis. The high dielectric permittivity of SnO2 doped TiO2 has been attributed to a special defect-dipole structure. Such dielectric behavior has been observed in this work in hydrogen-reduced TiO2–SnO2 crystals, where the colossal dielectric permittivity and the low loss factor of ~ 0.1 exist in the temperature range of 20–300 °C (and frequency at 10 ~ 105 Hz). Based on the investigations on the phase microstructures, the elemental valences, impedance spectroscopy and dielectric response, the colossal dielectric permittivity of the hydrogen-reduced TiO2–SnO2 crystals was thought to be associated with the electronic relaxation polarization mechanism. This research further revealed that the weak-binding electron is the most critical factor for the high dielectric permittivity in TiO2–SnO2 system, while a special defect-dipole structure may not be a preliminary determinant.