Thermal and Electrical Conductivity of Ge₁Sb₄Te₇ Chalcogenide Alloy

The unique properties of the Ge₁Sb₄Te₇ alloy as a chalcogenide make it a good candidate for application in phase-change random access memory as well as thermoelectric materials. The thermal and electrical conductivity of the Ge₁Sb₄Te₇ alloy play an important role in both applications. This work aims to determine the thermal conductivity and electrical resistivity of the Ge₁Sb₄Te₇ alloy as a function of temperature and to discuss the thermal conduction mechanism. Thermal conductivity and electrical resistivity were measured from room temperature to 778 K using the hot strip method and the four-terminal method, respectively. The thermal conductivity of the Ge₁Sb₄Te₇ alloy shows an interesting temperature dependence: it decreases up to about 600 K, and then increases with increasing temperature. The electrical resistivity shows a monotonic increase with increasing temperature. Through a discussion of the thermal conductivity results together with electrical resistivity results, it is proposed that electronic thermal conductivity dominates the thermal conductivity, while the bipolar diffusion contributes to the increase in the thermal conductivity at higher temperatures. The resonance bonding existing in this chalcogenide alloy accounts for the low lattice thermal conductivity.