Jump to main content
Jump to site search

Issue 7, 2003
Previous Article Next Article

Niobium pentoxide prepared by soft chemical routes: morphology, structure, defects and quantum size effect

Author affiliations

Abstract

Niobium pentoxide (Nb2O5) is prepared by soft chemical routes (digestion either in ammonia or in hydrazine solutions) and is compared to a commercial sample. According to various characterization methods (XRD, HRTEM, DTA-TG, UV-visible diffuse reflectance, Raman and EPR spectroscopies), Nb2O5 shows particular bulk and surface properties. The phase transformation temperatures (amorphous → pseudo-hexagonal, pseudo-hexagonal → orthorhombic and orthorhombic → monoclinic) for the synthetic Nb2O5 are about 100–150 °C higher than for the commercial sample. The textural properties depend strongly on the preparation method. After calcination at 400 °C, the sample prepared in ammonia has a larger pore volume (0.22 cm3 g−1) and a better resistance to sintering at 600 °C. The preparation in hydrazine gives the following advantages only if the gel is sonically redispersed in ethanol: low particle size, narrow size distribution, and higher resistance to sintering (140 m2 g−1 at 600 °C). Preparation in ammonia or in hydrazine favors the formation of defects, characterized by a significant absorption in the visible range adjacent to the interband transition (3.4 eV, 360 nm). These defects, which disappear upon heating in oxygen, are identified as Nb4+ species and ionized oxygen vacancies as confirmed by EPR measurements. Finally, the nanoparticles obtained by sonication in ethanol (average particle size 4.5 nm) shows a significant band gap increase (from 3.4 eV to 4.2 eV) which is assigned to a quantum size effect.

Back to tab navigation

Publication details

The article was received on 14 Oct 2002, accepted on 14 Feb 2003 and first published on 25 Feb 2003


Article type: Paper
DOI: 10.1039/B210055J
Phys. Chem. Chem. Phys., 2003,5, 1457-1466

  •   Request permissions

    Niobium pentoxide prepared by soft chemical routes: morphology, structure, defects and quantum size effect

    R. Brayner and F. Bozon-Verduraz, Phys. Chem. Chem. Phys., 2003, 5, 1457
    DOI: 10.1039/B210055J

Search articles by author

Spotlight

Advertisements