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GeO2 Doped Lithium Borophosphate Glasses
Authors: Mošner Petr | Vorokhta Maryna | Koudelka Ladislav | Moguš-Milanković Andrea | Montagne Lionel | Revel Bertrand
Year: 2013
Type of publication: ostatní - článek ve sborníku
Name of source: The 23rd International Congress on Glass 2013: Book of Abstracts
Publisher name: Česká sklářská společnost
Place: Teplice
Page from-to: 273
Titles:
Language Name Abstract Keywords
eng GeO2 Doped Lithium Borophosphate Glasses GeO2 containing lithium borophosphate glasses were studied in compositional series (100-x)[0.5Li2O-0.1B2O3-0.4P2O5]-xGeO2 with x = 0-25 mol% GeO2. Glasses were prepared by slow cooling of the melt in a graphite mould from the temperature region of 1000-1150oC and characterized by the measurements of density, molar volume and chemical durability. Thermal properties of glasses were investigated by DTA and TD methods; their structure was studied by Raman spectroscopy, 31P and 11B MAS NMR spectroscopy. The 31P MAS NMR spectra of the glasses show that with the replacement of the starting 50Li2O-10B2O3-40P2O5 composition by GeO2, the ratio of Q2 and Q1 units present in the structure slightly changes. The incorporation of germanate structural units was reflected in the middle-frequency part of the Raman spectra between 450 and 750 cm-1 by the presence of vibrational modes associated with P-O-Ge and Ge-O-Ge bonds. 11B MAS NMR spectrum of the starting 50Li2O-10B2O3-40P2O5 glass showed one narrow symmetrical signal, characteristic of BO4 units coordinated by four phosphorus atoms as B(OP)4. Germanium forms various mixed tetrahedral units with B-O-Ge bonds, where B(OP)4 structural units are gradually replaced by B(OP)4-n(OGe)n units. Increasing GeO2 content leads also to the partial transformation of BO4 into BO3 units in the glass structure. The incorporation of germanate structural units into the parent borophosphate glass results in a decrease of their molar volume and chemical durability while their density, glass transition temperature, dilatometric softening temperature and thermal stability increase. Thermal expansion coefficient obtained by TD measurements decreases slightly from 10.7 to 6.6 ppm °C-1 with increasing GeO2 content. Major compounds formed by crystallization of glasses were LiPO3, Li4P2O7, BPO4 and LiGe2(PO4)3.

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