Ti1−xVxO2 nanocrystals were prepared by employing a novel and water-soluble precursor via hydrothermal method, and the microstructure and magnetic properties have been investigated. All the samples belong to a pure anatase structure and exhibit room-temperature ferromagnetism (RTFM) without any trace of vanadium oxides or clusters. After V doping, the anatase structure is retained, while crystal growth is restrained. The homogenous distribution of V, in V4+ chemical state, in TiO2 lattice is confirmed by X-ray powder diffraction (XRD), energy-dispersive X-ray spectra (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Ferromagnetism in Ti1−xVxO2 is revealed to be highly dependent on the V content and defect concentrations. Furthermore, the annealing study in various atmospheres indicates that the oxygen vacancies and interstitials play a crucial role in inducing ferromagnetism in Ti1−xVxO2 system, and the origin of RTFM can be explained by bound magnetic polaron model.
[Show abstract][Hide abstract] ABSTRACT: The state and outlook of works on the creation of ferromagnetic semiconductor materials for applications in spin electronics and informatics units are considered. The obtained results on promising ferromagnetic semiconductor material classes—doped elementary semiconductors, AIIIBV compounds, and semiconductor oxides—are given. Unsolved problems in the considered area are indicated and possible ways of their solutions are outlined.
[Show abstract][Hide abstract] ABSTRACT: V-doped TiO2 nanoparticles were synthesized by sonochemical process using titanium isopropoxide as a titanium source, vanadyl acetylacetonate as a dopant source. Sonication was conducted using sonic horn operated at 20 kHz for 20 min until the completely precipitated product was reached. The as-synthesized precipitates with various vanadium dopant (1–5 mol %) were calcined at 500–1000 °C for 4 h. The relevant physical properties of the nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM). The anatase phase TiO2 nanoparticles can be synthesized by sonochemical process. Post calcinations process results in the anatase-to-rutile phase transformation and the enhancement in crystallinity with increasing temperature. The results also indicate good incorporation of V ions in TiO2 lattices and significant effect of V dopant on alternation of interplanar spacing of TiO2.
Ceramics International 05/2013; 39:S389–S393. DOI:10.1016/j.ceramint.2012.10.100 · 2.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study aims to investigate the power potential of Li-ion batteries using a hydrothermal process to synthesize nanoscale Nb–TiO2 with high surface area. By substituting Nb into anatase TiO2, the rate capability of Li-ion batteries is improved with the formation of nanoplate Nb–TiO2 containing (001) facets and NbOx species. In addition, the high solubility of Nb promotes the transformation of TiO2 from hollow-like to plate-like morphology, accelerating the Li-ion surface transportation over a large contact area. With respect to rate capability, Nb–TiO2 displays a high capacity of 220 mAh g−1 at 0.5C and retains 127 mAh g−1 at 10C. Additionally, the cyclability test exhibits less degradation after 10,000 cycles. In order to investigate the mechanisms of capability improvement, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are applied to measure the Li-ion diffusivity and surface charge-transfer resistance. The results demonstrate that both Li-ion diffusivity and surface charge-transfer ability are enhanced, leading to pseudocapacitance. Thus, it can be concluded that nanoplate Nb–TiO2 exhibits superior rate capability by the improvement of pseudocapacitance. This study derives a novel process to synthesize nanoplate TiO2 and should provide a potential approach for industrial fabrication of high power Li-ion batteries.
Journal of Power Sources 08/2015; 288. DOI:10.1016/j.jpowsour.2015.04.074 · 6.22 Impact Factor
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