Andriy Zakutayev1 Sebastian Siol1 Aaron Holder1 Brenden Ortiz2 Philip Parilla1 Eric Toberer2 1 Stephan Lany1

1, National Renewable Energy Laboratory, Golden, Colorado, United States
2, Colorado School of Mines, Golden, Colorado, United States

SnTe is a narrow band gap IV–VI semiconductor with potential for thermoelectric applications [1]. Recently, SnTe-based isovalent/heterostructural alloys, such as ternary SnTe-SnSe and SnTe-MnTe, have been demonstrated to have ZT up to 1.3 [2]. Following up on this work, we used a combination of theoretical and experimental methods to access solubility limits in quaternary Sn1-yMnySe1-xTex alloys [3]. Results from first principle calculations indicate low equilibrium solubility of x,y < 0.05 in Sn1-yMnySe1-xTex alloys, in good agreement with results obtained from bulk equilibrium synthesis experiments, and predict significantly higher spinodal decomposition limits. Experimental combinatorial screening using sputtered Sn1-yMnySe1-xTex thin films showed a remarkable increase in non-equilibrium solubility to over x,y > 0.2. These results were used to guide the bulk synthesis of metastable alloys, with similar high solubility limits achieved in ball milled Sn1-yMnySe1-xTex samples. The ability to reproduce the non-equilibrium solubility levels in bulk materials indicates that combinatorial growth can inform bulk synthetic routes. Furthermore, these results illustrate how computational and combinatorial-growth methods together can be used to study equilibrium and non-equilibrium solubility limits in complex alloys used in thermoelectric applications. Finally, the large difference between equilibrium and non-equilibrium solubility limits in Sn1-yMnySe1-xTex indicates these metastable alloys are attractive for controlled formation of nano-precipitates – a potential route to nanostructured thermoelectric materials with reduced thermal conductivity.
[1] J. Snyder et al, Appl. Phys. Lett., 2016, 109, 42102.
[2] M. G. Kanatzidis et al, J. Am. Chem. Soc., 2015, 137, 11507
[3] S. Siol, A.Holder, B. R. Ortiz, P. A. Parilla, E. Toberer, S. Lany, A. Zakutayev, RSC Adv., 2017, 7, 24747