%0 Journal Article %1 WOS:000086823700009 %A de Andrade, JS %A Pinheiro, AG %A Vasconcelos, IF %A de Araujo, MAB %A Valente, MA %A Sombra, ASB %C THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND %D 2000 %I PERGAMON-ELSEVIER SCIENCE LTD %J JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS %K KNbO3; ceramics} glasses; {ferroelectric %N 6 %P 899-906 %R 10.1016/S0022-3697(99)00387-X %T Structural studies of KNbO3 in niobate glass-ceramics %V 61 %X Potassium niobophosphate glasses and glass-ceramics of the family xNb(2)O(5).(50 - x)P2O5. 50K(2)O:yFe(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 Fe2O3 doping. From our Mossbauer analysis, high spin Fe2+ and Fe3+ 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 K4Nb6O17 and the ferroelectric KNbO3 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 Nb2O5/P2O5 leads the niobium to sites of octahedral symmetry and consequently to the formation of ferroelectric KNbO3, as seen by X-ray diffraction analysis. (C) 2000 Elsevier Science Ltd. All rights reserved.

@article{WOS:000086823700009, abstract = {Potassium niobophosphate glasses and glass-ceramics of the family [xNb(2)O(5).(50 - x)P2O5. 50K(2)O]:yFe(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 Fe2O3 doping. From our Mossbauer analysis, high spin Fe2+ and Fe3+ 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 K4Nb6O17 and the ferroelectric KNbO3 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 Nb2O5/P2O5 leads the niobium to sites of octahedral symmetry and consequently to the formation of ferroelectric KNbO3, as seen by X-ray diffraction analysis. (C) 2000 Elsevier Science Ltd. All rights reserved.}, added-at = {2022-05-23T20:00:14.000+0200}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, author = {de Andrade, JS and Pinheiro, AG and Vasconcelos, IF and de Araujo, MAB and Valente, MA and Sombra, ASB}, biburl = {https://www.bibsonomy.org/bibtex/2be3d934da37d048541bba724045b252b/ppgfis_ufc_br}, doi = {10.1016/S0022-3697(99)00387-X}, interhash = {76613a53b3a4aa0d379d724a8d551b58}, intrahash = {be3d934da37d048541bba724045b252b}, issn = {0022-3697}, journal = {JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS}, keywords = {KNbO3; ceramics} glasses; {ferroelectric}, number = 6, pages = {899-906}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, pubstate = {published}, timestamp = {2022-05-23T20:00:14.000+0200}, title = {Structural studies of KNbO3 in niobate glass-ceramics}, tppubtype = {article}, volume = 61, year = 2000 }