Thermophysical Properties And Conduction Mechanisms In AsXSe1-X Chalcogenide Glasses Ranging From X = 0.2 To 0.5

The arsenic (As) to selenium (Se) ratio in AsxSe1-x glasses ranging from x = 0.2 to 0.5 was varied in order to examin e the effect of chemical and topological ordering on the glass\u27 thermal transport behavior. The fundamental thermal properties of glass transition temperature (Tg), thermal conductivity (k), and heat capacity (cp) were experimentally measured using differential scanning calorimetry, transient plane source method, and ultrasonic testing. Based on topological constraint theory, inflections in Tg and k were found at the structural coordination number «r» of 2.4, whereas a slight increase in heat capacity (cp) with increasing «r» was observed. A maximum in total thermal conductivity of 0.232 W/m·K was measured for the composition with x = 0.4, which corresponds to the stoichiometric As2Se3. Gas kinetic theory was used to derive an expression for the photon (kp) portion of thermal conductivity, which was calculated by measurements of the glass\u27 absorption coefficient (α) and refractive index (n). Models based on Debye theory were used to derive expressions for specific heat (cv) and the lattice (kl) portion of thermal conductivity. The maximum value for kp was 0.173 W/m·K for the composition with x = 0.2, and a minimum value of 0.144 W/m·K was measured for the composition with x = 0.4. Photonic conduction was found to be the carrier mechanisms in all compositions, comprising 60% to 95% of the measured total thermal conductivity