| Autor: |
Caggiu, L., Iacomini, A., Pistidda, C., Farina, V., Senes, N., Cao, H., Gavini, E., Mulas, G., Garroni, S., Enzo, S. |
| Jazyk: |
angličtina |
| Rok vydání: |
2020 |
| Předmět: |
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| Zdroj: |
Caggiu, L.; Iacomini, A.; Pistidda, C.; Farina, V.; Senes, N.; Cao, H.; Gavini, E.; Mulas, G.; Garroni, S.; Enzo, S.: In situ synchrotron radiation investigation of V2O5–Nb2O5 metastable compounds: transformational kinetics at high temperatures with a new structural solution for the orthorhombic V4Nb20O60 phase. In: Dalton Transactions. Vol. 49 (2020) 48, 17584-17593. (DOI: /10.1039/d0dt03426f) |
| ISSN: |
1477-9226 |
| DOI: |
10.1039/d0dt03426f) |
| Popis: |
Due to the considerable interest in vanadium niobium oxides as a lithium storage material, the kinetics and transformation processes of the V2O5–5Nb2O5 system have been investigated by in situ synchrotron powder X-ray diffraction. The diffraction data after the thermal treatments selected with a view on the most significant features were supplemented with specific ex situ experiments conducted using a laboratory rotating anode X-ray diffractometer. The morphological changes of the mixed powders assuming an amorphous and nanocrystalline solid solution structure as a function of the temperature were inspected by scanning electron microscopy observations. The structural solution of the powder diffraction pattern of the phase recorded in situ at a temperature of about 700 °C was compatible with an orthorhombic crystal structure with the space group Amm2. The obtained lattice parameters for this structure were a = 3.965 Å; b = 17.395 Å, c = 17.742 Å, and the cell composition was V4Nb20O60, Pearson symbol oA84, and density = 4.10 g cm−3. In this structure, while the niobium atoms may be four-, five-, and six-fold coordinated by oxygen atoms, the vanadium atoms were six-fold or seven-fold coordinated. At the temperature of 800 °C and just above, the selected 1 : 2 and 1 : 3 V2O5–Nb2O5 compositions, respectively, returned mostly a tetragonal VNb9O25 phase, in line with earlier observations conducted for determination of the stability phase diagram of such quasi-binary systems. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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