Colossal dielectric behavior of Co-doped TiO₂ ceramics: A comparative study

The (Nb + In) co-doped rutile TiO₂ ceramics were synthesized by spark plasma sintering (SPS) and traditional solid-state sintering (TS) techniques, respectively. Highly-density co-doped rutile TiO₂ ceramics are prepared with the SPS method by 20 min, whereas it takes nearly 30 h with the TS method. It is observed that SPS ceramics showed smaller and uniform grain size, and better densification than TS counterparts. Both sets of the co-doped TiO₂ ceramics showed single rutile phase according to X-ray diffraction (XRD) results. X-ray photoelectron spectroscopy (XPS) is adopted to detect and compare the element-valence-state of both sets of the co-doped TiO₂ ceramics. The dielectric response, impedance spectroscopy (IS), and the effects of annealing treatment are systematically investigated, which could not only be helpful for optimizing their dielectric properties, but also shed the light on the colossal dielectric mechanism.