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Potassium niobato-phosphate glasses and glass-ceramics
Authors: Koudelka Ladislav | Kalenda Petr | Mošner Petr | Montagne Lionel | Revel Bertrand
Year: 2021
Type of publication: článek v odborném periodiku
Name of source: Journal of Non-Crystalline Solids
Publisher name: Elsevier Science BV
Place: Amsterdam
Page from-to: 121091
Titles:
Language Name Abstract Keywords
cze Draselná niobáto-fosfátová skla a sklokeramika Skla ternárního systému K2O-Nb2O5-P2O5 byla studována ve třech řadách. Teplota skelného přechodu v řadách A a B roste a růstem obsahu Nb2O5, zatímco v řadě C roste jen mírně. Index lomu roste výrazně pouze v řadách A a B s růstem obsahu Nb2O5. Struktura skel byla navržena na základě analýzy MAS NMR spekter jader 31P a Ramanových spekter. Ve skelch s obsahem 30-40 mol.% Nb2O5, Ramanova spektra ukázala na tvorbu vazeb Nb-O-Nb propojujících oktaedry NbO6 a dokonce na tvorbu niobátových 3D klastrů. Vzorky s obsahem méně než 30 mol.% P2O5 jevily tendenci ke tvorbě skelně-krystalických materiálů obsahujících krystaly niobičnanu draselného. fosfátová skla; vlastnosti skel; struktura; NMR spektra; Ramanova spektra
eng Potassium niobato-phosphate glasses and glass-ceramics Glasses of the ternary system K2O-Nb2O5-P2O5 were studied in three compositional series (60-x)K2O-xNb2O540P2O5 (series A) with 10-40 mol% Nb2O5, 40K2O-yNb2O5-(60-y)P2O5 (series B) with 10-30 mol% Nb2O5 and zK2O-20Nb2O5-(80-z)P2O5 (series C) with 20-50 mol% K2O. The basic physical parameters of glasses were also determined. Almost all the glasses were colourless, only two glasses with a higher Nb2O5 content were blue coloured due to the presence of a small amount of Nb4+ ions. The glass transition temperature in the series A and B increases with increasing Nb2O5 content, whereas in series C it increases only slightly. The highest value of 757 degrees C was found for the glass 20K2O-40Nb2O5-40P2O5 from the A series. The refraction index only increases significantly in the glasses of the series A and B with increasing Nb2O5 content; glass 20K2O-40Nb2O5-40P2O5 from the series A had the highest value of 1.809 at 587.6 nm. The glass structure was evaluated from an analysis of their 31P MAS NMR and Raman spectra. The efficiency of Raman scattering by NbO6 units is higher than that of PO4 units, which results in the suppression of phosphate vibrational bands in the Raman spectra of glasses with a higher Nb2O5 content. In the glasses with 30-40 mol% Nb2O5, Raman spectra showed on the formation of chains Nb-O-Nb interconnecting NbO6 octahedra and even on the formation of 3D niobate clusters. Samples containing less than 30 mol% P2O5 revealed a tendency to form glass-crystalline materials containing potassium niobate crystals. Their crystalline structure was not identified, but according to their Raman spectra, they contain NbO6 octahedra similar to those in KNbO3. Phosphate glasses; Glass  properties; Glass structure; NMR spectra; Raman spectra

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