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1996 (1)
1Author    W. J. Bresser, J. Wells, M. Zhang, P. BoolchandRequires cookie*
 Title    Molecular Origin of Glass Forming Tendency in Ternary Te-Se-Br(Cl) Chalcohalide Glasses  
 Abstract    Bulk glasses of Te 3 _-Se-(CI or Br) 2+V , the composition spanning the glass forming range, were characterized by differential scanning calorimetry, l2r, Te absorption, and 129 I emission Mössbauer spectroscopy. The results reveal that the stoichiometric glasses Te 3 (Cl or Br) 2 consists of c-Te 3 Cl 2 -like chain fragments about 1.5 nm long and terminated by one-fold coordinated halogen atoms. The 12:i Te electric hyperfine structure results reveal that Te replacement by Se (z =/ 0) leads to preferential occupancy at those Te sites in the chains that are two-fold coordinated, and in a rather striking fashion demonstrate that the average length of the chain fragments remains independent of Se concentration. Halogen atoms in the glasses act as chain terminators, and also bond to Te-sites in the chains to produce four-fold coordinated sites. The low glass transition temperatures (7g ~ 70 -90°C), the low average coordination number of the proposed chain-fragments, along with the hyperfine structure results, suggest that the extensive glass forming tendency in the chalcohalides derives from the floppiness of the chain-fragments. 
  Reference    Z. Naturforsch. 51a, 373—380 (1996); received January 5 1996 
  Published    1996 
  Keywords    ^Te Absorption Mössbauer Spectroscopy, 129 I Emission Mössbauer Spectroscopy, Chalcohalide Glasses, Molecular Structure, Glass Formation 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0373.pdf 
 Identifier    ZNA-1996-51a-0373 
 Volume    51