Excess vibrational modes and high thermoelectric performance of the quenched and slow-cooled two-phase alloy Cu_(0.2)Ag _(2.8)SbSeTe_2

摘要

In this article we examine the low-temperature specific heat of slow-cooled Cu_ (0.2)Ag_(2.8)SbSeTe_2 and the thermoelectric performance of quenched samples. We find that the low-temperature specific heat is dominated by two Einstein terms of approximate energies of 2.5 and 5meV. The specific-heat behavior is consistent with the amorphous low-temperature thermal conductivity behavior and validates the glassy nature of the structure. We performed the synthesis of quenched samples in an attempt to eliminate the presence of micro-cracks, whose existence presumably enhances electronic scattering. We find that quenching eliminates the presence of micro-cracks but does not result in an improvement of the figure of merit. Specifically, the highest ZT obtained in the quenched samples (ZT = 1.5), though very competitive, is still significantly less that the ZT obtained in the slow-cooled samples (ZT = 1.75).