Thermal studies of the effect of thallium in ternary Ge-Te-Tl chalcogenide glasses

• Published in: Journal of materials science. Materials in electronics 2021, Vol.32 (1), p.853-860
• Main Authors: Rahman, Mohammad Mahbubur, Rukmani, K., Sekar, Rajam, Asokan, S.
• Format: Article
• Language: English
• Subjects: Bond energy; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composition; Crystallization; Enthalpy; Glass transition temperature; Heat transmission; Materials Science; Optical and Electronic Materials; Parameter estimation; Switching; Tellurium; Temperature; Thallium; Thermodynamic properties
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-020-04863-w

Alternating differential scanning calorimetric (ADSC) studies have been carried out on bulk Ge 17 Te 83-x Tl x glasses over a wide range of compositions (0 ≤ x ≤ 13), to estimate the thermal parameters and also to understand the effect of thallium addition on the non-isothermal crystallization process. It is found that glass transition temperature (T g ) decreases with increasing thallium concentration, indicating decrease in network connectivity with thallium addition. The decrease in T g is large in the composition range 0 ≤ x ≤ 6 and much less for compositions x ≥ 7. The observed composition dependence of T g is similar to the variation in switching voltages with composition and is in close agreement with the variation in the average bond energy. Further, two crystallization temperatures (T c1 and T c2 ) have been observed in Ge 17 Te 83-x Tl x glasses, in the composition range 2 ≤ x ≤ 10, which indicates that glasses in this range are phase separated. As these glasses are tellurium rich, it is probable that the regions formed by Te- chains crystallize first and the rest of the matrix crystallizes later. The change in enthalpy due to non-reversing part of the heat flow is very small and fairly constant over the entire range of glasses studied. This indicates that structural re-organization is easy in this system which agrees well with the memory type electrical switching observed in these samples.