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 diffracti
on, Mossbauer, infrared and Raman scattering spectroscopy. For the potassiu
m-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 a
morphous structural neighborhood. The precipitation of crystalline K4Nb6O17
and the ferroelectric KNbO3 crystals was confirmed by X-ray powder diffrac
tion in the samples with x = 40 and 50 mol%, respectively. The infrared and
Raman scattering spectroscopy results suggest that the increase of the rat
io Nb2O5/P2O5 leads the niobium to sites of octahedral symmetry and consequ
ently to the formation of ferroelectric KNbO3, as seen by X-ray diffraction
analysis. (C) 2000 Elsevier Science Ltd. All rights reserved.