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Structure and Properties of Silver Borophosphate Glasses Modified by TeO2
Autoři: Vorokhta Maryna | Mošner Petr | Koudelka Ladislav | Černošek Zdeněk
Rok: 2013
Druh publikace: ostatní - článek ve sborníku
Název zdroje: The 23rd International Congress on Glass 2013: Book of Abstracts
Název nakladatele: Česká sklářská společnost
Místo vydání: Teplice
Strana od-do: 270
Tituly:
Jazyk Název Abstrakt Klíčová slova
eng Structure and Properties of Silver Borophosphate Glasses Modified by TeO2 The work deals with the study of the effect of TeO2 on the structure and properties of silver borophosphate glasses prepared in compositional series (100-x)[0.5Ag2O-0.1B2O3-0.4P2O5]-xTeO2 in a concentration range of x = 0-80 mol% of TeO2. Glasses were characterized by the measurements of density, molar volume and chemical durability. Thermal properties were investigated by DTA, TD and HMTA methods. Their structure was studied by Raman spectroscopy. The obtained Raman spectra showed that the structure of 50Ag2O-10B2O3-40P2O5 glass is formed especially by metaphosphate structural units (Q2) and diphosphate structural (Q1) units connected through P-O-P bridges. The replacement of PO4 structural units by tellurate units is accompanied by the gradual depolymerization of phosphate chains. At a high TeO2 content isolated PO4 tetrahedra are predominantly formed in the structure of glasses. Tellurium oxide is incorporated in the structural network in the form of TeO3 trigonal pyramids and TeO4 trigonal bipyramids. The ratio of TeO4/TeO3 structural units increases with increasing TeO2 content. The incorporation of TeOx structural units into the starting 50Ag2O-10B2O3-40P2O5 borophosphate glass results in a gradual decrease of their molar volume within the range of 39.2-30.8 cm3 mol-1 while their density increases. All glasses exhibit good chemical durability against water corrosion. Thermoanalytical measurements showed that most of prepared glasses crystallize under heating in the temperature range of 410-520°C and the surface nucleation mechanism prevails over the internal one. The highest thermal stability and the lowest tendency towards crystallization were observed for the glasses with nominal TeO2 contents between 40 and 60 mol% TeO2. Glass transition temperature and dilatometric softening temperature increase with increasing TeO2 content, whereas thermal expansion coefficient decreases.