Page 63 - Chalcogenide Glasses for Infrared Optics

Chalcogenide Glasses 41

500

400

Softening point (°C) 300

200
As S 3
2

100
100 200 300
Knoop hardness
FIGURE 2.13 Correlation of softening point and Knoop hardness for
chalcogenide glasses.

four elements. Even with a softening point of 500°C, Knoop hardness
was less than 250.

2.5.2 Thermal Coefficients of Expansion
The higher the softening point, the smaller the thermal expansion
coefficient. Results obtained from 30 samples are plotted in Fig. 2.14.
The correlation is very general in part because the glasses measured
are from different systems some with four elements. Many factors
may affect results.

2.5.3 Density
The densities of selenium and tellurium glasses containing silicon,
germanium, arsenic, and phosphorus are almost a linear function of
the calculated average molecular weight of the glass composition.