• • Chemical bonding and crystal structure dictate intrinsic lattice thermal conductivity (κL) in p-type Mg3Sb2; layered Zintl structure yields intrinsically low κL (~1 W/m·K at 300 K), critical for mid-temperature (500–700 K) waste heat recovery.
• • Point defect engineering via Mg-site doping (e.g., Ag, Zn) and Sb-site doping (e.g., Bi) reduces κL by up to 50% (e.g., from 1.2 to 0.6 W/m·K at 300 K), directly enhancing zT by 30–50% in p-type compositions.
• • Dual-site co-doping (e.g., Li and Cd) synergistically optimizes hole concentration (up to ~10^20 cm^-3) and introduces multi-scale phonon scattering, achieving peak zT >1.0 at 700 K, a benchmark for p-type Mg3Sb2.
• • Advanced preparation technologies (e.g., melt spinning, spark plasma sintering) refine grain size to <1 μm, reducing κL further via grain boundary scattering, with reported κL as low as 0.5 W/m·K at 300 K, enabling higher device efficiency.