Structural changes in thermoelectric SnSe at high pressures

Abstract

Abstract. The crystal structure of the thermoelectric material tin selenide has been investigated with angle-dispersive synchrotron x-ray powder diffraction under hydrostatic pressure up to 27 GPa. With increasing pressure, a continuous evolution of the crystal structure from the GeS type to the higher-symmetry TlI type was observed, with a critical pressure of 10.5(3) GPa. The orthorhombic high-pressure modification, β -SnSe, is closely related to the pseudo-tetragonal high-temperature modification at ambient pressure. The similarity between the changes of the crystal structure at elevated temperatures and at high pressures suggests the possibility that strained thin films of SnSe may provide a route to overcoming the problem of the limited thermal stability of β-SnSe at high temperatures.

Pressure-Stabilized Tin Selenide Phase with an Unexpected Stoichiometry and a Predicted Superconducting State at Low Temperatures

“…As expected, SnSe goes through a phase transition from the P nma structure through Cmcm to a higher symmetry B2 structure with increasing pressure. The high-pressure crystal structures and the corresponding phase transition pressures are in good agreements with experimental observations [6,7], indicating the reliability of our calculations. SnSe 2 has a CdI 2 -type structure with a space group of P3m1 at 0 GPa, and it transforms to the R3m space group at 5 GPa.…”

“…SnSe is a narrow band gap semiconductor with an unprecedented thermoelectric efficiency [4,5]. It was shown that laminar SnSe (B16-type structure in the P nma space group) undergoes a pressure-induced structural phase transition to the B33 structure (Cmcm space group) at about 10.5 GPa [6]. Under further compression, SnSe transforms to the B2 structure (P m3m space group) and this phase was found to exhibit a superconducting transition at low temperatures above 58 GPa [7].…”

Phonon anharmonicity and negative thermal expansion in SnSe

“…This phase transition has been the subject of a number of early crystallographic and thermomechanical experimental investigations [22][23][24][25][26][27][28][29][30][31]. More recently, the ultra-low lattice thermal conductivity of SnSe has attracted great interest for thermoelectric applications, and has been studied both experimentally and through ab-initio simulations [10,[18][19][20][32][33][34][35][36][37][38][39][40][41][42]. The coupling between lattice distortion and electronic structure was recently shown to be responsible for the large anharmonicity, which persists in a broad range of temperatures, and leads to the low thermal conductivity [10,17].…”

Engineering the Near-Edge Electronic Structure of SnSe through Strains

“…In order to further optimize the performance and extend the range of working temperature of SnSe, several approaches have been explored, for example, hole doping [1], applying hydrostatic pressure [7,8], and nanostructuring [9,10]. Another important alternative is strain-engineering, which has long been used as an effective and predictable means for tuning the materials properties [11][12][13][14][15][16], including strain-induced structural phase transitions [17][18][19], indirect-direct band gap transition [11][12][13], and semiconductormetal transition [12,20].…”