Effect of Cr\(^{3+}\) Concentration and Heat-treating Temperature on Structural Property of Cr\(^{3+}\)- doped TiO\(_2\) Nanowires Synthesized by Hydrothermal Method

Abstract

Anatase Ti_1-xCr_xO₂ nanowires with Cr³⁺ dopant contents ranging from x = 0 to 0.1 have been successfully synthesized by hydrothermal method. The nanowires were prepared from anatase titanium dioxide powder (TiO₂), chrome nitrate (Cr(NO₃)₃), and sodium hydroxide (NaOH). The effect of the Cr³⁺ concentration and heat-treating temperature on structure, morphology of the synthesized Ti_1-xCr_xO₂ samples has been studied by X-ray diffraction, scanning electron microscopy and Raman scattering. At low heat-treating temperature (≤ 600 ^oC), the samples exhibited anatase phase and in the Raman spectra of samples with x ≥ 0.01 exhibited a new series peak at 120, 236, 250, 292, 362, 430, 467 and 550 cm^-1, which were assigned to the localized vibrational modes related to the complexes containing Cr³⁺ ion. But at high heat-treating temperature (1100 ^oC), the samples exhibited rutile phase, in the Raman spectra the above-mentioned peak series did not appear, instead of this, only observed shifting and broadening of characteristic Raman modes (E_g and M) for rutile TiO₂ with increasing Cr³⁺ dopant content, which proves that the Cr³⁺ ions have replaced the Ti⁴⁺ ions in the rutile TiO₂ host lattice. The lattice constants of both the rutile and anatase TiO₂ crystallites have been hardly affected by Cr³⁺ ions dopant contents.