Thermoelectric performance optimization of GeMnSbTe compounds through increasing the Mn solid solubility: Effects of the co-doping of rare earth elements

GeTe is a p-type thermoelectric (TE) material that exhibits a high ZT value and holds promise for a wide range of applications. In this study, a series of Ge0.86Mn0.1Sb0.04Te + 1 mol.% RE (Rare Earth elements = Er, Tm, Yb, Lu) compounds are synthesized through the melt-quenching method followed by fast-hot-pressing. Findings indicate that the TE properties are improved by simultaneously increasing the Seebeck coefficient and reducing the thermal conductivity, making the peak ZT value experiences an enhancement of 73%, while the average ZT value through 450-800 K shows an improvement of 70%. The solid solubility of Mn is significantly increased by the addition of the REs, that promotes the regulating effect of Mn on the energy band. A diverse range of microstructures including ordered atomic staggered arrays, van der Waals interstitials, dislocation enrichment, dislocation networks, nano precipitation phases with cavity structures, interstitial clusters, and vacancy clusters are introduced by REs, significantly contributing to the reduction of the kappa L. Thus, this study offers valuable insights and mechanism analysis into enhancing the properties of GeMnSbTe materials by incorporating REs, and proves that Tm has better thermoelectric performance optimization effect in this.