An International Research Journal

AJP Vol 9 No 3, 2000


SSN : 0971 - 3093

Vol  9, No. 3, July-September, 2000

Asian Journal of Physics                                                                                                          Vol. 9, No 3 (2000) 709-721

The Maximum in Glass Transition Temperature (Tg) near x = 1/3 in GexSe1-x Glasses


Department of Electrical, Computer Engineering and Computer Science,
University of Cincinnati, Cincinnati, OH 45221-0030, USA


We review results of Raman scattering, Mössbauer spectroscopy and T-modulated Differential Scanning Calorimetry experiments on GexSe1-x glasses. The molecular origin of the maximum in Tg near x=1/3 or mean coordination r- =2(1+x)=2.67. suggested by these experiments, implies that a nanoscale phase separation of the glass network takes place into Se-rich (A) and Ge-rich (B) molecular clusters. Phase separation on a molecular scale initiates at x > 0.31, and the B phase becomes the dominant one for x >0.35. In particular, in contrast to α - and β -  crystalline GeSe2, stoichiometric GeSe2 glass is neither chemically ordered nor a continuous network. In ternary GexAsySe1-x-y, glasses at x=y, such nanoscale phase separation is apparently suppressed by chemical alloying As for r- up to 3.0. and Tgs are found to increase continuously with r-

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