As-S-Te系ガラスの熱膨脹とその関連特性

抄録

The following thermal properties of As-S-Te glasses were determined from the thermal expansion mesurements: Transformation temperatures (T_g), temperatures of initial deformation under load, i.e., softening temperatures (T_s), and average linear thermal expansion coefficients in the ranges from room temperature to T_g (α_l) and from T_g to T_s (α_h). The measurements were made through the entire range of vitrification. The observed values of T_g, T_s and α_l were in the ranges of 28°-182°C, 69°-227°C and (1.75-6.30)×10^-5cm/cm/°C, respectively. The dependence of these properties on composition of As-S-Te glasses was dissimilar to the previously reported results of both As-S and Si-As-Te glasses: The linear relationship was not observed in the present results between the properties and the covalent bond concentration calculated by ignoring the bond species. These results can be explained by an interpretation described in the following paragraphs in consideration of the effect of the bond species formed by tellurium component introduced into As-S parent glasses on intermolecular forces in the glass structure.
When the (S/As) atomic ratio was considerably larger than 1.5, both T_g and T_s increased and α_l decreased with increasing tellurium content up to 10 atom.%, whereas the reverse and/or little changes were observed when the tellurium content was increased further. These behaviors may be connected with the change in intermolecular force due to the formation of partially polar Te-S bonds and the successive formation of non-polar Te-Te bonds in glass.
When the (S/As) ratio was slightly larger than 1.5, the decrease of both T_g and T_s and no appreciable change of α_l were observed with increasing tellurium content up to 10 atom.%. For glasses of the (S/As) ratio less than 1.5, the decrease of both T_g and T_s and the increase of α_l were observed with increasing tellurium content up to 10 atom.%. These behaviors may be attributed to the formation of Te-Te bonds and/or As-Te bonds which leads to the decrease of crosslinkages in the glasses.
The observed values of α_h fluctuated in the range of (4-15)×10^-5cm/cm/°C. The fluctuation may be possibly associated with the elastic after-effect, and the interpretation for the dependence of α_h on composition has not been given for the present glasses.