Thermal, Structural, and Crystallization Properties of New Tantalum Alkali‐Germanate Glasses. Issue 7 (23rd April 2015)

• Record Type: Journal Article
• Authors: de Pietro, Gabriele Matinatti; Pereira, Camila; Gonçalves, Rogeria Rocha; Ribeiro, Sidney J. L.; Freschi, Carolina Dakuzaku; Cassanjes, Fábia Castro; Poirier, Gael; Pinckney, L.
• Is Part Of: Journal of the American Ceramic Society. Volume 98:Issue 7(2015)
• Page Start: 2086
• Page End: 2093
• Publication Date: 2015-04-23
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.13555
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace13555-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>In this work, new glass compositions were prepared in the ternary system GeO<sub>2</sub>–K<sub>2</sub>O–Ta<sub>2</sub>O<sub>5</sub>. Potassium oxide was added to reach the complete melt of the starting mixture and two composition series were investigated: the first one with a constant K<sub>2</sub>O molar content of 10% in the ternary system (90–<italic>x</italic>)GeO<sub>2</sub>–10K<sub>2</sub>O–<italic>x</italic>Ta<sub>2</sub>O<sub>5</sub> and the second one with the same molar content of K<sub>2</sub>O and Ta<sub>2</sub>O<sub>5</sub> in the ternary system (100–2<italic>x</italic>)GeO<sub>2</sub>–<italic>x</italic>K<sub>2</sub>O–<italic>x</italic>Ta<sub>2</sub>O<sub>5</sub>. Homogeneous and transparent glasses could be obtained between <italic>x</italic> = 0 and 20. X‐ray diffraction analyzes of samples with <italic>x</italic> = 25 identified orthorhombic Ta<sub>2</sub>O<sub>5</sub> in the first series and an isostructure of K<sub>3.8</sub>Ge<sub>3</sub>Nb<sub>5</sub>O<sub>20.4</sub> in the second series where it is assumed that Ta<sup>5+</sup> ions are inserted in the Nb<sup>5+</sup> sites. As one of our goal with these materials is related with the preparation of glass‐ceramics containing Ta<sub>2</sub>O<sub>5</sub> nanocrystals, the first series has been selected for further characterizations. An increase in glass‐transition temperatures with increasing Ta<sub>2</sub>O<sub>5</sub> content as well as an increase of the thermal stability from <italic>x</italic> = 0 to 10 has been identified by differential scanning calorimetry. For higher contents, crystallization events were identified. Fourier transform infrared and Raman spectroscopic characterizations allowed to point out the intermediary behavior of Ta<sub>2</sub>O<sub>5</sub> in the vitreous network where TaO<sub>6</sub> octahedra are inserted inside the germanate network with TaO<sub>6</sub> clusters identified at higher Ta<sub>2</sub>O<sub>5</sub> contents. Heat‐treated samples with high tantalum contents (<italic>x</italic> = 15 and 20) exhibit preferential precipitation of orthorhombic Ta<sub>2</sub>O<sub>5</sub> with nanometric size, suggesting the possibility of obtaining transparent glass‐ceramics for optical applications.</p> </abstract>