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The physicochemical basis of the exothermic effect at DTA and DSC curves below glass transition temperature in chalcogenide and oxide glass forming substances

V. S. MINAEV1,* , S. P. TIMOSHENKOV2, V. V. KALUGIN2, S. I. KOVALEV2, S. N. NOVIKOV2, V. P. VASILIEV3

Affiliation

  1. State Unitary Company Science Production Center «Spurt», Research Institute of Material Science and Technology, passage 4806, h. 4/2, Zelenograd, 124460, Moscow, Russian Federation
  2. Moscow Institute of Electronics Engineering (Technical University), passage 4806, h. 5, Zelenograd, 124498, Moscow, Russian Federation
  3. Faculty of Chemistry, Moscow State University, Vorob’evy gory, 119992, Moscow, Russian Federation

Abstract

Endothermic effect of glass transition, fixed by means of DTA and DSC at glass heating is well-known. In some cases these methods record also exothermic effect that appears both at glass heating and at melt cooling. Now there is no clear understanding of physicochemical essence of this effect. The analysis of structure of various crystal polyforms, glass forming liquid, glass of individual chemical substances (ICS), able to form glass Se, GeS2, As2Se3, H2O, Ca (PO3) 2, etc., made on base polymeric-polymorphous concept of a glass and glass forming liquids structure shows that the ex-effect below Тg is a result of a transformation of the structural fragments from glass, which have no long-range order (polymorphoids) of high-temperature polymorphous modifications (HTPM) into low-temperature polymorphous modifications (LTPM). The effect in glass is originally connected with similar effect in crystal which is the result of polymorphous transformation HTPM → LTPM..

Keywords

Glass transition, Exotermic effect, Polymorphous modifications, Polymorphoid..

Submitted at: July 5, 2009
Accepted at: Dec. 10, 2009

Citation

V. S. MINAEV, S. P. TIMOSHENKOV, V. V. KALUGIN, S. I. KOVALEV, S. N. NOVIKOV, V. P. VASILIEV, The physicochemical basis of the exothermic effect at DTA and DSC curves below glass transition temperature in chalcogenide and oxide glass forming substances, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 12, pp. 1950-1953 (2009)