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Potassium niobophosphate glasses and glass-ceramics of the family [xNb2O5.(50-x) P2O5.50K2O]:yFe2O3 were studied by x-ray powder diffraction, infrared and Raman scattering spectroscopy. For the potassium-phosphate samples [50P2O5-50K2O] the iron oxide presents a network former behaviour, for 2 mol% of Fe2O3 doping. The precipitation of crystalline K4Nb6O17 and 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.

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