Studies of the temperature dependence of the short range structure and local dynamics in silver borate glasses

Author： Dalba G. Fornasini P. Grisenti R. Beccara S. A Daldosso N. Sanson A. Rocca F. Monti F. Kuzmin A.

ISSN： 0031-9090

Source： Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B, Vol.44, Iss.2, 2003-04, pp. : 75-78

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Abstract

EXAFS temperature dependent measurements have been carried out on the borate glass doped with silver iodide, (AgI)_0.55(Ag₂O.4B₂O₃)_0.45, at the K-edges of Ag and I, in the range 39-500 K. Local negative thermal expansion has been measured in the explored temperature range; in the same range, crystalline AgI shows a positive trend. This behaviour, already found for another silver borate glass containing a higher content of silver iodide, was interpreted in terms of a relaxing of the AgI amorphous network within the silver borate host matrix. In the light of the results obtained for the glass (AgI)_0.55(Ag₂O.4B₂O₃)_0.45, having a much lower AgI concentration and showing an almost equal thermal expansion, a different interpretation is now necessary.The Ag-I first shell distance contraction is a specific characteristic of the AgI amorphous network within the silver borate host matrix: temperature increase favours shorter average distance of the mobile Ag⁺ cations from I ions. The host matrix influences, however, the local thermal disorder around Ag and I species.