Thermoelectricpropertiesof（GeTe）1-x[（Ag2Te）0.4（Sb2Te3）0.6]xalloys

The （GeTe）x（Ag Sb Te2）100-xalloys （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～2/3has 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～0.7W·m-1·K-1in the entire temperature range and the lowest one of only 0.45 W·m-1·K-1is achieved due to additional phonon scattering by point defects.As a result,a peak thermoelectric figure of merit （zT） of～1.80 and an average one of～1.37 in 300–800 K are realized in nonstoichiometric TAGS alloys here.