91 / 2025-03-13 15:06:15

Pressure induced amorphization and recrystallization of thermoelectric material AgSbTe2

Thermoeletric materials,High pressure,Pressure induced amorphization and recrystallization,Laser heating,Solid solution

¹Guangdong Technion-Institute of Technology GTIIT, Department of Material Science and Engineering, Shantou, People’s republic of China

²Technion-Institute of Technology, Department of Material Science and Engineering, Haifa, State of Israel

³Guangdong Provincial Key Laboratory of Materials and Technologies for Energy Conversion, Shantou, People’s republic of China



sun06604@gtiit.edu.cn, amouyal@technion.ac.il, elissaios.stavrou@gtiit.edu.cn





    Thermoelectric (TE) materials, which can directly convert thermal energy to produce electrical energy and vice-versa, emerging with considerable promise. The thermoelectric performance of material is characterized by dimensionless figure of merit ZT [1-3].  

AgSbTe₂ attracts a lot of attention in recent years for its high ZT value 2.6 at 573K by cadmium doping [4]. A promising, yet relatively unexplored, avenue for advancing TE materials involves optimizing their parameters through applied stress or pressure. High-pressure methods provide access to a unique realm where variable pressure can be applied to tailor thermoelectric properties.

    Previous studies of AgSbTe₂ under pressure contradicted on the overall structural evolution, mainly about the exact structure of the higher-pressure phase [5,6]. In this study, we performed a synchrotron X-ray powder diffraction study using a Diamond anvil cell (DAC) and Neon as the pressure transmission medium (PTM) to apply pressure on AgSbTe₂. The pressure was increased from ambient to 60 GPa. At ambient conditions, AgSbTe₂ crystalizes in a FCC-like partial solid solution, in which Ag and Sb atoms occupy the 4a Wyckoff positions (WP) with 50% occupancy. Upon pressure increase, a pressure induced amorphization was observed at 19.2 GPa, and AgSbTe₂ remained amorphous up to 37 GPa. Above 37 GPa, a pressure induced crystallization was observed towards a BCC-like structure. At room temperature, the XRD patterns of the BCC phase strongly indicated a total solid solution, with all elements occupying the 2a WP with relevant partial occupancies (25, 25 and 50% for Ag, Sb and Te, respectively).  In order to further explore the validity of this structural model, after AgSbTe₂ crystalized into the BCC-like structure, we used laser heating to examine the possible ordering of the structure at elevated temperatures. A previous study on Bi-Te alloys documented that temperature could induced some atomic ordering [7]. However, in our study even the temperature was increased to 1700K which decomposed the material into Sb₂Te₃ and Ag₂Te, we didn’t observe the characteristic Bragg peak of a partial solid solution (B2 structure). Therefore, in contrast to the pervious report by Kumar et al. [6] we conclude that the BCC structure is a total solid solution (A2 structure), as opposed to a partial solid solution B2 structure.

    Upon decreasing pressure, a clear kinetic effect was observed. In details, the rate of releasing pressure dictates if the phase transitions are fully reversible towards the FCC-like structure or the amorphous phase persists after full pressure release. Molecular dynamics calculations aiming to fully elucidate the overall structural evolution under pressure are ongoing.



[1] Liu, W., Hu, J., Zhang, S., Deng, M., Han, C. G., & Liu, Y. (2017). New trends, strategies and opportunities in thermoelectric materials: A perspective. Materials Today Physics, 1, 50-60.

[2] Zhang, Q., Li, X., Kang, Y., Zhang, L., Yu, D., He, J., ... & Xu, B. (2015). High pressure synthesis of Te-doped CoSb₃ with enhanced thermoelectric performance. Journal of Materials Science: Materials in Electronics, 26, 385-391.

[3] Gao, J., Mao, T., Lv, T., Li, Z., & Xu, G. (2018). Thermoelectric performance of n-type (PbTe)_{1− x} (CoTe)_x composite prepared by high pressure sintering method. Journal of Materials Science: Materials in Electronics, 29, 5327-5336.

[4] Roychowdhury, S., Ghosh, T., Arora, R., Samanta, M., Xie, L., Singh, N. K., ... & Biswas, K. (2021). Enhanced atomic ordering leads to high thermoelectric performance in AgSbTe₂. Science, 371(6530), 722-727.

[5] Ko, Y. H., Oh, M. W., Lee, J. K., Park, S. D., Kim, K. J., & Choi, Y. S. (2014). Structural studies of AgSbTe₂ under pressure: Experimental and theoretical analyses. Current Applied Physics, 14(11), 1538-1542.

[6] Kumar, R. S., Cornelius, A. L., Kim, E., Shen, Y., Yoneda, S., Chen, C., & Nicol, M. F. (2005). Pressure induced structural phase transition in AgSbTe₂. Physical Review B, 72(6), 060101.

[7] Loa, I., Bos, J. W., Downie, R. A., & Syassen, K. (2016). Atomic ordering in cubic bismuth telluride alloy phases at high pressure. Physical Review B, 93(22), 224109.