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Structure and properties of barium niobophosphate glasses
Authors: Koudelka Ladislav | Kalenda Petr | Mošner Petr | Montagne Lionel | Revel Bertrand
Year: 2017
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: 68-74
Titles:
Language Name Abstract Keywords
cze Struktura a vlastnosti niobofosfátových skel barnatých Byla studována fosfátová skla systému BaO-Nb2O5-P2O5 ve dvou kompozičních řadách 40BaO-xNb2O5-(60-x)P2O5 (řada A), kde x = 0-40 mol% Nb2O5, a yBaO-20Nb2O5-(80-y)P2O5 (řada B), kde y = 20-60 mol% BaO. Bylo připraveno celkem devět homogenních skel v obou řadách a byly stanoveny jejich základní parametry (hustota, molární objem, teplota skelné transformace, dilatometrická teplota měknutí a koeficient teplotní roztažnosti). Skla mají vysokou chemickou odolnost a teplota skelné transformace v řadě A roste s růstem obsahu Nb2O5 z hodnoty 324°C až na 727°C, zatímco v řadě B s růstem obsahu BaO hodnot Tg roste v interval 620-725°C. Index lomu roste výrazněji v řadě A než v řadě B. Podle Ramanových spekter se při nízkém obsahu Nb2O5 tvoří izolované oktaedry NbO6, které se při vyšších obsazích tohoto oxidu propojují vazbami -Nb-O-Nb-O- do řetězců. fosfátová skla; oxid niobičný; termická analýza; Ramanova spektra; NMR spektra
eng Structure and properties of barium niobophosphate glasses Phosphate glasses of the ternary system BaO-xNb(2)O(5)-P2O5 were studied in two compositional series, namely 40BaO-xNb(2)O(5)-(60-x)P205 (series A), with x = 0-40 mol% Nb2O5, and yBaO-xNb(2)O(5)-(80-y)P2O5 (series B), with y = 20-60 mol% BaO. Nine homogeneous glassy samples were prepared altogether in both series, and their basic physical properties (density, molar volume, glass transition temperature, dilatometric softening temperature and thermal expansion coefficient) were determined. The chemical durability of the Nb2O5-containing glasses is high and the dissolution rate at 80 degrees C is lower than 4-5 x 10(-8)g cm(-2) min(-1). The glass transition temperature of the glasses in series A increased significantly with increasing Nb2O5 content from 324 to 727 degrees C, whereas in the series B with increasing BaO content, Tg increased within the range 620-725 degrees C. The index of refraction increased more steeply in glass series A with increasing Nb2O5 content than in the glass series B. According to the Raman spectra in the glass series A, at low Nb2O5 content niobium forms isolated octahedra NbO6 incorporated in the glass network, but when Nb2O5 content increases, these octahedra are linked into chains and further into three-dimensional clusters. In glass series B, NbO6 octahedra form only Nb O Nb-O-chains connecting NbO6 octahedra. NbO6 octahedra clustering is reflected also in the 31P MAS NMR spectra of BaO-Nb2O5-P2O5 glasses showing on a non-monotonous transformation of phosphate units in the direction Q(3) -> Q(2) -> Q(1) -> Q(0), both with increasing Nb2O5 content in the first A series and BaO content in the second B series. Phosphate glasses; Niobium oxide; Thermal analysis; Raman spectra; NMR spectra

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