Crystallization of monoclinic WO3 in tungstate fluorophosphate glasses |
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Authors: | Gaël Poirier Fábia C Cassanjes Sidney JL Ribeiro |
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Institution: | a Departamento de Ciências Exatas, UNIFAL-MG, CEP 37130-000, Alfenas-MG, Brazil b Laboratory of Photonic Materials - Instituto de Química - UNESP, P.O. Box 355, CEP 14800-900, Araraquara - SP, Brazil |
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Abstract: | Tungstate fluorophosphate glass compositions with high WO3 concentration were prepared in the ternary system (80−0.8x)NaPO3-(20−0.2x)BaF2-xWO3 with x = 40,50 and 60 mol%. Transparency decreases as WO3 concentration increases but can be improved by addition of oxidizing systems such as CeO2 or Sb2O3/NaNO3. Characterizations by thermal analysis (DSC) point out that an increase in the amount of WO3 results in a higher glass transition temperature. In addition, such compositions are very stable against devitrification since samples containing 40% and 50% of WO3 donot even exhibit the expected crystallization event. In these samples, the stability against crystallization decreases with the WO3 content and vitreous sample containing 60% of WO3 exhibits an endothermic event around 620 °C due to crystallization of monoclinic WO3 phase. In these glasses, it was shown that the nucleation stage can be induced by thermal-treatment when external nucleating agents such as Ti or Sb are used. Finally, gold-doped samples exhibit a higher crystallization tendency and monoclinic WO3 phase can be grown in such glasses. |
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Keywords: | 61 43 Fs 65 60 +a 61 10 &minus i |
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