Dielectric response of Cr ̵ doped TiO_2 nanoparticles: Effect of doping concentration and annealing temperature

Abstract

The combined effect of doping chromium (Cr) as well as annealing temperature on the dielectric spectroscopy performance of titanium (TiO_2)was investigated. Accordingly, two series of chromium doped titania samples with the form 〖(Ti〗_(1-x) Cr_x O_2) where x=0-25 mol% were fabricated utilizing the hydrolysis method. The first series was used as-synthesized while the second series was used after annealing at 500 ℃ for 1h . The microstructure of both synthesized series was characterized by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET). The (XRD) result confirms the formation of the amorphous characteristics of such pure and Cr doped TiO_2 (as-synthesized) and crystaline characteristics of such pure and Cr doped TiO_2 (annealed at 500 ℃ for 1h ). The average crystallite size in second series (annealed at 500 ℃) as estimated by the Scherrer’s equation varies in the range of ~12–30 nm on doping of Cr ions in TiO_2. The measured surface area of TiO_2 is decreased by Cr doping in first series (as-synthesized) while it is increased by Cr doping in second series (annealed at 500 ℃). The variation in both dielectric constant (e^'), and ac conductivity (σ_ac) as a function of applied frequency at different doping concentration of Cr were investigated. The measurements confirms that both e^' and σ_ac values of TiO_2 were decreased with Cr doping in first series and increased with Cr doping in second series.