Kinetics of relaxation and crystallization of sodium metaphosphate glass

Kinetics of structural relaxation and crystallization of NaPO3 glassforming melt is studied by means of thermal analyses. It is demonstrated that activation energy depends strongly on fictive temperature T-f. The dependence of the onset temperature T-o of the glass transition interval on the heating rate q(+) is investigated for samples that were previously cooled down at a rate q(-) of about 850 K/min. The dimensionless fragility F is a measure of the dependence of the activation energy for spatial rearrangement on the changes of structure. According to the present results F is large for NaPO3 (i.e. phosphates are 'fragile' substances). (C) 2008 Elsevier B.V. All rights reserved.