About this Abstract |
| Meeting |
MS&T26: Materials Science & Technology
|
| Symposium
|
2026 Graduate Student Poster Contest
|
| Presentation Title |
SPG-21: Phase Transitions and Local Structure in Ca1-xSrxAgSb |
| Author(s) |
Amir Sam l62358303 Mohammadzadeh Shirazi, Alexandra Zevalkink, Ashiquzzaman Shawon, Raphael Hermann, Eric Toberer |
| On-Site Speaker (Planned) |
Amir Sam l62358303 Mohammadzadeh Shirazi |
| Abstract Scope |
The AMX Zintl phases exhibit structural versatility that enables targeted tuning of dimensionality and symmetry for optimizing thermoelectric performance. We investigate the Ca1−xSrxAgSb solid solution, which spans three structural archetypes: 3D orthorhombic, buckled corrugated hexagonal, and planar flat hexagonal. Polycrystalline Ca1−xSrxAgSb (0 ≤ x ≤ 1.0) samples were synthesized by solid-state reaction. X-ray diffraction reveals a composition-driven evolution from orthorhombic (x ≈ 0.0), through corrugated intermediate phase (x ≈ 0.2-0.3), to flat hexagonal phase (x > 0.5). Annealing near the orthorhombic-corrugated boundary drives transformation to the corrugated phase, indicating metastability. Temperature-dependent neutron powder diffraction on Ca0.2Sr0.8AgSb shows a smooth corrugated-to-flat transition near 700K. Molecular dynamics simulations and pair distribution function analysis reveal persistent local Ag disorder despite the average flat hexagonal symmetry, demonstrating that local structural distortions persist beyond the average crystallographic structure. Elastic, thermal, and electronic transport measurements establish structure-property relationships across these composition and temperature driven polymorphic transitions. |