The kinetics of phase transitions in bismuth-modified selenide glasses As_xSe_100-x-yBi_y as studied by differential thermal analysis and exoelectron emission

Chem. Met. Alloys 4 (2011) 22-25

https://doi.org/10.30970/cma4.0140

Czesław GÓRECKI, Tadeusz GÓRECKI

The kinetics of the glass transition (retrification) in bismuth-modified selenide glasses As_xSe_100-x-yBi_y (x = 10.2, 8, 6 and y = 0, 2, 4) have been investigated by parallel differential thermal analysis (DTA) and exoelectron emission (EEE) measurements. EEE is a surface effect connected with structural transformations in the surface layer, whereas the DTA measurements give information about transformations occurring in the bulk of the sample. It was found that the phase transitions occurring in the investigated selenide glasses are evidenced by anomalies in the temperature dependence of both the EEE intensity and DTA curves. Consequently, the validity of the DTA and EEE techniques for studies of phase transitions in vitreous chalcogenide semiconductors has been demonstrated. Admixture of bismuth causes a significant lowering of the temperature of the retrification process, both in the surface layer and in the bulk. It causes a decrease of the activation energy for the retrification process on the surface as well as in the bulk, reducing the thermal stability of the investigated materials. A more detailed comparison of the DTA traces indicates that the areas under the endotherms of the samples containing Bi are systematically (by about 36 %) lower than those of the corresponding samples without Bi.

Ozawa plots for the surface (EEE) and volume (DTA) retrification temperatures of the As₆Se₉₀Bi₄ glass.

Keywords

Chalcogenide glasses / Exoelectron emission / Activation energy / Retrification