Thermoelectric properties of (GeTe)1-x[(Ag2Te)0.4(Sb2Te3)0.6]x alloys

The (GeTe)(x)(AgSbTe2)(100-x) alloys (TAGS-x) have been demonstrated as a promising p-type candidate for thermoelectric applications, attracting numerous attentions on the advancements of thermoelectric performance. Manipulation of carrier concentration for optimizing thermoelectric performance in TAGS can be achieved by varying the ratio of Ag to Sb, and the Ag/Sb ratio of similar to 2/3 has been proven as the optimal composition. Therefore, this work focuses on the systematic investigation on thermoelectric properties of (GeTe)(1-x)[(Ag2Te)(0.4)(Sb2Te3)(0.6)](x) alloys. The crystal structure for the alloys transfers from rhombohedral to cubic at room temperature as x >= 0.2. The evolution of band parameter is estimated using a single parabolic band (SPB) model with acoustic phonon scattering. The density of states effective mass increases with x increasing, which leads to an enhancement of Seebeck coefficient along with a reduction in Hall mobility due to the additional carrier scattering by point defects. Meanwhile, the lattice thermal conductivity of lower than similar to 0.7 W.m(-1).K-1 in the entire temperature range and the lowest one of only 0.45 W.m(-1).K-1 is achieved due to additional phonon scattering by point defects. As a result, a peak thermoelectric figure of merit (zT) of similar to 1.80 and an average one of similar to 1.37 in 300-800 K are realized in nonstoichiometric TAGS alloys here. Graphic abstract

Automated summary

The research focuses on the systematic investigation of the thermoelectric properties of (GeTe)(1-x)[(Ag2Te)(0.4)(Sb2Te3)(0.6)](x) alloys, discovering that increasing the value of x in the alloy can enhance the Seebeck coefficient but reduce the Hall mobility. Furthermore, additional phonon scattering caused by point defects can lower the lattice thermal conductivity, thereby improving thermoelectric efficiency.