| Autor: |
de Andrade, J.S, Pinheiro, A.G, Vasconcelos, I.F, de Araújo, M.A.B, Valente, M.A, Sombra, A.S.B |
| Zdroj: |
Journal of Physics and Chemistry of Solids; June 2000, Vol. 61 Issue: 6 p899-906, 8p |
| Abstrakt: |
Potassium niobophosphate glasses and glass-ceramics of the family [xNb2O5·(50−x)P2O5·50K2O]:yFe2O3were studied by X-ray powder diffraction, Mössbauer, infrared and Raman scattering spectroscopy. For the potassium–phosphate samples [50P2O5–50K2O], the iron oxide presents a network forming behavior for 5mol% of Fe2O3doping. From our Mössbauer analysis, high spin Fe2+and Fe3+in a distorted octahedral coordination are present in all samples. One can conclude from the Mössbauer parameters that iron is present in a very broad site distribution, which is characteristic of an amorphous structural neighborhood. The precipitation of crystalline K4Nb6O17and the ferroelectric KNbO3crystals was confirmed by X-ray powder diffraction in the samples with x=40 and 50mol%, respectively. The infrared and Raman scattering spectroscopy results suggest that the increase of the ratio Nb2O5/P2O5leads the niobium to sites of octahedral symmetry and consequently to the formation of ferroelectric KNbO3, as seen by X-ray diffraction analysis. |
| Databáze: |
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