Excellent giant dielectric properties over wide temperatures of (Al, Sc)3+ and Nb5+ doped TiO2

Abstract

The dielectric properties of TiO2 triple–doped with Al3+/Sc3+/Nb5+ (ASNTO) prepared by a conventional mixed route were studied. Pure rutile–TiO2, highly dense microstructure and all elements homogeneously dispersed were observed. The existence of oxygen vacancies was investigated using Raman spectroscopy. The Ti3+ ions and free–electrons in the structure were confirmed. The great improvement of the dielectric properties was obtained with high dielectric constant (ε′ > 104) and low loss (tanδ < 0.03). Furthermore, the temperature coefficient of ε′ was less than ±15% over the temperature range from −60 to 210 °C. Interestingly, at 210 °C, a low tanδ ∼ 0.05 was also obtained. Furthermore, the ε′ value was slightly dependent on the DC bias filed up to 25 V⋅mm−1. The ASNTO was electrically homogeneous, which consisted of the insulating and semiconducting parts. The obtained dielectric properties were mainly caused by the interfacial polarization. The low tanδ and narrow temperature coefficient of ε′ could be described by an ultra–high resistance of the insulating parts.