|About this Abstract
||2021 TMS Annual Meeting & Exhibition
||Alloys and Compounds for Thermoelectric and Solar Cell Applications IX
||Size Effects in the High-pressure Behavior of Layered AM2X2 Compounds
||Wanyue Peng, Mario Calderon, Benjamin Brugman, Gill Levental, Ashiwini Balodhi, Megan Rylko, Susannah Dorfman, Alexandra Zevalkink
|On-Site Speaker (Planned)
AM2X2 layered compounds are a promising class of thermoelectric materials. Typically, for traditional layered compounds, the out-of-plane direction is significantly more compressible than the in-plane direction due to the relatively weak interlayer bonding. However, this is not necessarily true for complex layered structures. In the present study, we used high-pressure synchrotron X-ray diffraction to study a series of layered compounds with the trigonal CaAl2Si2 structure. Our results show that compounds with small cations (e.g. A = Mg) have near-isotropic compressibility, whereas larger cations exhibit anisotropic behavior akin to more traditional layered compounds. This is consistent with previously reported DFT and experimental transport properties in single crystals. Furthermore, new displacive phase transitions were observed in several AM2X2 compounds under high-enough pressures. Interestingly, although MgMg2Sb2 and MgMg2Bi2 show near-isotropic compressibility in their ambient phase, different directions of the unit cell undergo drastically different changes upon the displacive phase transition.