Network topological thresholds in gallium doped As–Te glasses – Electrical and thermal investigations

Electrical switching and differential scanning calorimetric studies are undertaken on bulk As20Te80−xGax glasses, to elucidate the network topological thresholds. It is found that these glasses exhibit a single glass transition (Tg) and two crystallization reactions (Tc1 & Tc2) upon heating. It is also found that there is only a marginal change in Tg with the addition of up to about 10% of Ga; around this composition an increase is seen in Tg which culminates in a local maximum around x = 15. The decrease exhibited in Tg beyond this composition, leads to a local minimum at x = 17.5. Further, the As20Te80−xGax glasses are found to exhibit memory type electrical switching. The switching voltages (VT) increase with the increase in gallium content and a local maximum is seen in VT around x = 15. VT is found to decrease with x thereafter, exhibiting a local minimum around x = 17.5. The composition dependence of Tc1 is found to be very similar to that of VT of As20Te80−xGax glasses. Based on the present results, it is proposed that the composition x = 15 and x = 17.5 correspond to the rigidity percolation and chemical thresholds, respectively, of As20Te80−xGax glasses.