Glasses And Calorimetry Lab Report

. Experimental

Glasses of (Se60Te40)xTl(100-x) composition were prepared from mixture of high pure (99.999%) Se, Te and Tl where (x=80, 75, 70 and 60). The appropriate proportions in at% were weighed and sealed in quartz ampoules (12 mm diameter) under vacuum of 10−5 Torr. Each sample was cooked for 24 h at temperature  1000 oC. The ampoules were frequently shaken to homogenize the melt. Quenching was done in ice water to get the glassy state. The densities (ρ) of the glasses under test were measured at room temperature by Archimedes technique using xylene as immersion liquid, and the molar volume values were then calculated using the relation, VM=MT/(ρ), where, MT is the total molecular weight. The average coordination number (L) was also calculated using the standard method described in Refs. [14, 15]. For the composition (SeaTeb)cTld, L is given by: ( 1 ) where CN(Se)=2, CN(Te)=2

The obtained DSC characteristic curves of the investigated samples are presented in Fig. 3a. The values of the glass transition temperature (Tg), the onset temperature of crystallization (Tc) and the peak temperature of crystallization (Tp) are determined and listed in Table 2. Very weak (Tg) endothermic changes are observed for all the samples except for the sample (Se60Te40)75Tl25. On the other hand, a sharp exothermic (Tc) peaks are easily observed for all the samples except for the sample (Se60Te40)60Tl40 in which a weak (Tc) peak is observed. Abdel-Wahab et al. [26], reported a Tg = 99 ◦C and Tc = 152 ◦C for a Ge5Te20Se75 glass. Also, for a system of the composition As20Se(80-x)Tlx with (x= 5-35) which investigated by Dongol et al [16], Tg was found to decrease from 82 ◦C to 74 ◦C with the increase of x% content, also, a fluctuations in the Tc values from 125 ◦C to 340 ◦C was