Thermochimica Acta, Vol.523, No.1-2, 116-123, 2011
Which glass stability criterion is the best?
In order to investigate which glass stability criterion (G-criterion) is the best, we analyzed the following criteria: K(H), gamma, gamma(m), beta, beta', alpha, Phi, zeta, omega and omega(2). All these criteria are expressed through temperature relationships: r = T(x,c)/T(g) and m = T(l,m)/T(g) where T(g) is glass transition temperature, T(x) is the onset of the crystallization peak (or T(c) is the maximum of the crystallization peak), and T(l) is liquidus temperature (or T(m) melting temperature). First, we considered the values of the R(2) factor of correlation between G-criteria and critical cooling rate R(c). By expressing the G-criteria via r and m we established the relationships between them. These relations show that there may exist a potential linear dependence between gamma and gamma(m), as well as between gamma and beta', omega, omega(2) and zeta. Further, the sensitivity of G-criteria is a necessary condition for determining the differences between different glasses. We also analyze how big the statistical deviations are in relation to the calculated values for the normalized and non-normalized G-criteria. The linear dependent criteria have a very similar R(2) factor of correlation with R(c) and in that respect they are equal. Among them, omega(2) shows the best value of R(2). In relation to the accordance of the calculated and experimental values of the normalized G(n)-criteria, the statistical deviation strongly depends upon the choice of the point where it is assumed that G(n) is zero. If we compare the experimental values and the values which are calculated from the line determined by two given points, gamma is the best criterion. The gamma parameter has the lowest sensitivity in relation to the changes of both super cooled region and reduced glass transition temperature. Our conclusion is that from all the analyzed criteria there is not one which can be declared the best. In the case we have to make a choice, omega(2) is the best criterion, in addition to gamma(m). The reason for this fact is that omega(2) has the biggest R(2) factor of correlation with R(c) and also high sensitivity. (C) 2011 Elsevier B.V. All rights reserved.