Structural studies of KNbO 3 in niobate glass-ceramics
| Autor: | M. A. B. de Araújo, M.A. Valente, A. G. Pinheiro, J S de Andrade, Antonio Sergio Bezerra Sombra, Igor F. Vasconcelos |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Materials science
Mössbauer effect Niobium Infrared spectroscopy chemistry.chemical_element General Chemistry Condensed Matter Physics Ferroelectricity Amorphous solid symbols.namesake Crystallography chemistry Mössbauer spectroscopy symbols General Materials Science Raman spectroscopy Powder diffraction |
| Zdroj: | Journal of Physics and Chemistry of Solids. 61:899-906 |
| ISSN: | 0022-3697 |
| DOI: | 10.1016/s0022-3697(99)00387-x |
| Popis: | Potassium niobophosphate glasses and glass-ceramics of the family [ x Nb 2 O 5 ·(50− x )P 2 O 5 ·50K 2 O]: y Fe 2 O 3 were studied by X-ray powder diffraction, Mossbauer, infrared and Raman scattering spectroscopy. For the potassium–phosphate samples [50P 2 O 5 –50K 2 O], the iron oxide presents a network forming behavior for 5 mol% of Fe 2 O 3 doping. From our Mossbauer analysis, high spin Fe 2+ and Fe 3+ in a distorted octahedral coordination are present in all samples. One can conclude from the Mossbauer parameters that iron is present in a very broad site distribution, which is characteristic of an amorphous structural neighborhood. The precipitation of crystalline K 4 Nb 6 O 17 and the ferroelectric KNbO 3 crystals was confirmed by X-ray powder diffraction in the samples with x =40 and 50 mol%, respectively. The infrared and Raman scattering spectroscopy results suggest that the increase of the ratio Nb 2 O 5 /P 2 O 5 leads the niobium to sites of octahedral symmetry and consequently to the formation of ferroelectric KNbO 3 , as seen by X-ray diffraction analysis. |
| Databáze: | OpenAIRE |
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