Enhanced Structural Stability of Sb₂Se₃ via Pressure-Induced Alloying and Amorphization

Abstract

In this work, we revealed that Sb 2 Se 3 has one second-order isostructural phase transitions before it eventually transformed into a site-disordered alloy during compression. Then, a rare amorphization of alloy was discovered with decreasing pressure in Sb 2 Se 3 by performing in situ high-pressure X-ray diffraction (XRD) and Raman experiments, which may be owed to the significant difference in atomic electronegativity of Sb 2 Se 3 . Compared to the original structure, the amorphous phase of Sb 2 Se 3 is more stable at high pressure. Surprisingly, the structural stability of amorphous Sb 2 Se 3 at varying temperatures was also significantly improved via recompression. Our findings will provide insight into the formation mechanism of the bcc alloys and amorphization in A 2 B 3 (A = Sb, Bi; B = S, Se, Te) compounds and, especially, offer a new way to prepare amorphous materials. ■ INTRODUCTIONGenerally, amorphous materials can be obtained by rapid solidification of vapors and the melts, 1−3 which have been recognized and widely employed in the field of material science. In addition, several alternative routes have been constructed, such as gas absorption of metal alloys, 4−6 mechanical alloying, 7,8 anomalous diffusion, 9 or pulsed laser irradiation, 10 etc. Compared to these traditional methods, pressure-induced amorphization is more complex and unique and has been observed in various elements, 11−15 compounds, 16−22 and alloys. 23−25 However, almost all of these transformations are found in the compression process, so far widely unknown to the crystalline-to-amorphous transition with releasing pressure. Here, we find that a Sb-Se amorphous phase can be synthesized by pressurizing and depressurizing Sb 2 Se 3 .As typical A 2 B 3 -form (A = Sb, Bi; B = S, Se, Te) compounds, Sb 2 Se 3 has attracted a lot of interest due to the interesting properties for several applications, such as thermoelectric devices, 26 solar cells, 27 optical recording material, 28 and hydrogen storage materials, 29 etc. In recent years, Bi 2 Te 3 , Sb 2 Te 3 , and Bi 2 Se 3 have been experimentally observed as the simplest 3D topological insulators, 30,31 which make A 2 B 3 became a hot topic in the field of material research. External pressure can be used to tune the electronic and atomic structures of materials. It has been verified that the thermoelectric properties of Bi 2 Te 3 , Bi 2 Se 3 , and Sb 2 Te 3 can be improved under high pressures. 32−35 Also, pressure-induced electronic topological transitions (ETTs), 36−40 superconductivity, 41−47 and metallization transitions 48−50 of these compounds have also been extensively investigated. However, compared to the sufficient high-pressure studies of rhombohedral forms of A 2 B 3 (Bi 2 Te 3 , Sb 2 Te 3 , and Bi 2 Se 3 ), 39,45,51−59 the Pnma types of A 2 B 3 (Bi 2 S 3 , Sb 2 S 3 , and Sb 2 Se 3 ) have not received similar attention because of the lack of topological properties, and their structural transformations at high pressure are still indistinct. By a combination of high-pressure X...

Pressure-induced phase transitions, amorphization and alloying in Sb2S3

“…To the best of our knowledge, the site-disordered bcc structure or the substitutional solid-solution alloy has been observed for Bi 2 Te 3 , Sb 2 Te 3 , and Sb 2 Se 3 at high pressures, 28,30,32,37,38 but these are unprecedented for Bi 2 Se 3 , Bi 2 S 3 , Bi 2 O 3 , Sb 2 S 3 , and Sb 2 O 3 . Run 4 shows that a recompression may promote the transformation from the amorphous Sb 2 S 3 to the bcc alloy.…”

“…Similar behaviors have been observed for other A 2 B 3 compounds, which can be attributed to an isostructural transition caused by a pressure induced ETT. 17,29,32,33,[35][36][37][38] Subsequently, a second compressibility change between 27.3 GPa and 29.1 GPa could be attributed under the non-hydrostatic conditions 52 or the lattice distortion during amorphization of Sb 2 S 3 . The fitting of the P-V data (before and after the two discontinuous changes) to a Birch-Murnaghan Equation of State 53 yielded volume and bulk moduli of V 0 = 492 (1) Å 3 and B 0 = 38.3(5) GPa (the orange solid line), V 0 = 482.2 (3) Å 3 and B 0 = 50(2) GPa (the magenta solid line), and V 0 = 405.6(4) Å 3 and B 0 = 172(6) GPa (the wine solid line), with B 0 0 fixed as 4.…”

“…More importantly, the decrease is irreversible; therefore, after full release from the amorphous state, the Sb 3+ LEP activity in Sb 2 S 3 should already be low. Because the electronegativity of S is far larger than that of Sb, part of the transferred charges will be captured around S, 38 even if the pressure is fully released. These two factors combined results in the transition-pressure alloying of Sb 2 S 3 via recompression being much lower than that of Sb 2 Se 3 .…”

“…Further compression causes Bi 2 S 3 to undergo structural disorder and amorphization, 17 whereas Sb 2 Se 3 is eventually transformed into a substitutional solid solution. 37,38 However, the structural behavior of Sb 2 S 3 under pressure is more complicated, and diverse results have been reported.…”

Theoretical study of the stability of the tetradymite-like phases of Sb$_2$S$_3$, Bi$_2$S$_3$, and Sb$_2$Se$_3$

“…27,28 However, one study observed a pressureinduced isostructural phase transition at 12 GPa and a further tran- sition to a disordered Im-3m structure above 50 GPa, followed by a pressure-induced amorphization on releasing the pressure. 29 Despite the apparent stability of the Pnma phase, experimental highpressure studies have also found that Pnma-type Sb 2 Se 3 becomes a topological superconductor at 2.5 K and around 10 GPa, 30 exhibiting highly-conducting spin-polarized surface states similar to those observed for Bi 2 Se 3 . 31 Furthermore, a recent study has claimed to have synthesized the R-3m structure of Sb 2 Se 3 by atomic layer epitaxy on a buffer layer of Bi 2 Se 3 .…”