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Structure-property relationships in BaO-Nb2O5-P2O5 glasses
Autoři: Kalenda Petr | Koudelka Ladislav | Mošner Petr | Montagne Lionel | Revel Bertrand
Rok: 2017
Druh publikace: ostatní - přednáška nebo poster
Strana od-do: nestránkováno
Tituly:
Jazyk Název Abstrakt Klíčová slova
eng Structure-property relationships in BaO-Nb2O5-P2O5 glasses Phosphate glasses of the ternary system BaO-Nb2O5-P2O5 were studied in three compositional series, namely 40BaO-xNb2O5-(60-x)P2O5 (series A), with x = 0-40 mol% Nb2O5, and yBaO-20Nb2O5-(80-y)P2O5 (series B), with y = 20-60 mol% BaO and (100-z)[0.5BaO-0.5P2O5]-zNb2O5 (series C), with z = 0-50 mol% Nb2O5. Fourteen homogeneous glassy samples were prepared altogether in these series, and their basic physical properties (density, molar volume, glass transition temperature, dilatometric softening temperature and thermal expansion coefficient) were determined. Chemical durability of the Nb2O5-containing glasses is high and the dissolution rate at 80°C is lower than 4-5x10-8 g cm-2 min-1. The glass transition temperature of glasses in the series A increased significantly with increasing Nb2O5 content from 324 to 727°C. In the series B with increasing BaO content Tg increased within the range 620-725°C and in the series C within the range 463-739°C. The index of refraction increased more steeply in glass series A and C with increasing Nb2O5 content than in the glass series B with increasing BaO content. According to the Raman spectra in the glass series A and C at low Nb2O5 content niobium forms isolated NbO6 octahedra incorporated into the glass network. When Nb2O5 content increases, these octahedra are linked into chains and further into three-dimensional clusters. In the glass series B, NbO6 octahedra form only -Nb-O-Nb-O- chains connecting NbO6 octahedra. The 31P MAS NMR spectra of BaO-Nb2O5-P2O5 glasses show on a non-monotonous transformation of phosphate units in the direction Q3→Q2→Q1→Q0, both with increasing Nb2O5 content in the A and C series and with BaO content in the B series.