The results showed that the samples heat-treated at low temperature (≤600 ◦C) exhibited anatase phase and for Cr3+-doped anatase TiO2 samples with x ≥ , Raman spectra showed a new series of peaks 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+ ions. The samples heat-treated at high temperature (1100 ◦C) exhibited rutile phase. It was observed that the characteristic Raman modes (Eg and M) for rutile TiO2 were shifted and broadened with increasing Cr3+ dopant content. | Communications in Physics, Vol. 24, No. 4 (2014), pp. 353-362 DOI: EFFECT OF Cr3+ CONCENTRATION AND HEAT-TREATMENT ON STRUCTURAL PROPERTY OF Cr3+ -DOPED TiO2 NANOWIRES SYNTHESIZED BY HYDROTHERMAL METHOD TRINH THI LOAN AND NGUYEN NGOC LONG Faculty of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam E-mail: longnn@ Received 09 July 2014 Accepted for publication 24 October 2014 Abstract. Anatase Ti1−x Crx O2 nanowires with Cr3+ dopant contents ranging from x = 0 to have been successfully synthesized by hydrothermal method. The nanowires were prepared from anatase titanium dioxide (TiO2 ) powders, chromium nitrate (Cr(NO3 )3 ), and sodium hydroxide (NaOH). The effect of the Cr3+ concentration and heat-treating temperature on crystal structure, morphology and Raman spectra of the synthesized Ti1−x Crx O2 samples has been studied in detail by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The results showed that the samples heat-treated at low temperature (≤600 ◦ C) exhibited anatase phase and for Cr3+ -doped anatase TiO2 samples with x ≥ , Raman spectra showed a new series of peaks 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+ ions. The samples heat-treated at high temperature (1100 ◦ C) exhibited rutile phase. It was observed that the characteristic Raman modes (Eg and M) for rutile TiO2 were shifted and broadened with increasing Cr3+ dopant content. This phenomenon proves that the Cr3+ ions have replaced the Ti4+ ions in the rutile TiO2 host lattice. It was found that the lattice constants of both the rutile and anatase TiO2 were not changed when Cr3+ dopant contents were varied. Keywords: TiO2 :Cr3+ nanowires, hydrothermal method, structural property. I. INTRODUCTION In recent years, the nanometer-sized materials have attracted considerable attention because of
