Redox Behavior of Molybdenum and Tungsten in Phosphate Glasses

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• 作者：Ga&euml ; l Poirier ; Fabiola S. Ottoboni ; Fá ; bia Castro Cassanjes ; Á ; damo Remonte ; Younes Messaddeq ; Sidney J. L Ribeiro
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：April 17, 2008
• 年：2008
• 卷：112
• 期：15
• 页码：4481 - 4487
• 全文大小：253K
• 年卷期：v.112,no.15(April 17, 2008)
• ISSN：1520-5207

文摘

In this work, vitreous samples were prepared in the binary system (100 - x)NaPO₃-xMO₃ with M = Moand W and x varying from 10 to 60. The transmittance properties in the UV, visible, and near-infrared weremonitored as a function of MO₃ concentration. In both cases, an increase in the amount of transition metalresults in an intense and broad absorption band in the visible and near-infrared attributed to metal reductionunder synthesis conditions. It was shown that this large absorption can be partially or totally removed usingspecific oxidizing agents or by improving synthesis parameters such as melting temperature or cooling rateof the melt. In addition, structural investigations by Raman and X-ray absorption spectroscopy suggest thatreduction only occurs when the metal cation is in octahedral geometry and that the transmittance improvementis not related with any structural changes. These results were explained in terms of thermodynamic equilibriumof redox species in the melt and allowed to obtain for the first time transparent and chemically stable glassescontaining high concentrations of MO₃ with transition metals in octahedral geometry inside the glass network.