Thermal stability and crystallization kinetics of Bi doped Si15Te85-xBix (0 ≤ x ≤ 2) chalcogenide glassy alloys

Abstract

Bulk Si<inf>15</inf>Te<inf>85-x</inf>Bi<inf>x</inf> (0 ≤ x ≤ 2) chalcogenide glassy alloys were prepared by well-established melt quenching technique. Thermal stability and crystallization kinetics of these alloys were investigated by employing differential scanning calorimetry (DSC) technique at different heating rates, namely, 10, 15, 20 and 25 K/min under non-isothermal condition. Thermal parameters such as glass transition (<inf>Tg</inf>), onset crystallization (<inf>Tc</inf>) and peak crystallization (<inf>Tp</inf>) temperatures were observed. Double crystallization peaks observed in the DSC thermogram refer to the instability and phase separated network in the glasses. Various kinetic parameters such as thermal stability (ΔT), enthalpy (Δ<inf>Hc</inf>), entropy (ΔS), specific heat (Δ<inf>Cp</inf>) and fragility index are deduced. The calculated kinetic parameters suggest that the stability of glassy samples decreases with the increase in Bi addition. The activation energies of glass transition (<inf>Eg</inf>), and crystallization (<inf>Ec</inf>) are calculated using relevant kinetic formulae. We further discuss on the kinetics of the synthesized materials relevant for their applications in phase change memory (PCM) material. © 2017 Elsevier Ltd.