Infoscience

Journal article

Synthesis and Phase Stability of Metastable Bixbyite V2O3 Colloidal Nanocrystals

We have recently developed a colloidal route to vanadium sesquioxide (V2O3) nanocrystals with a metastable bixbyite crystal structure. In addn. to being one of the first reported observations of the bixbyite phase in V2O3, it is also one of the first successful colloidal syntheses of any of the vanadium oxides. The nanocrystals, measuring 5 to 30 nm in diam., possess a flower-like morphol. which densify into a more spherical shape as the reaction temp. is increased. The bixbyite structure was examd. by X-ray diffraction and an aminolysis reaction pathway was detd. by Fourier transform IR spectroscopy. A direct band gap of 1.29 eV was calcd. from optical data. Under ambient conditions, the structure was found to expand and become less distorted, as evidenced by XRD. This is thought to be due to the filling of structural oxygen vacancies in the bixbyite lattice. The onset of the irreversible transformation to the thermodynamically stable rhombohedral phase of V2O3 occurred just under 500 °C in an inert atm., accompanied by slight particle coarsening. A crit. size of transformation between 27 and 42 nm was estd. by applying the Scherrer formula to analyze XRD peak widths during the course of the transformation. The slow kinetics of transformation and large crit. size reveal the remarkable stability of the bixbyite phase over the rhombohedral phase in our nanocrystal system.

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