Low-dimensional engineering to enhance the thermoelectric properties and plasticity of bulk Mg₃Bi₂: A first-principles study

Mg₃Bi₂ is a promising eco-friendly layered thermoelectric material, yet it exhibits limited plasticity and thermoelectric performance in flexible thermoelectric device applications. In this work, we adopt low-dimensional engineering strategies with different crystal planes and layer thicknesses to investigate the structural stability, electronic structure, mechanical properties and thermoelectric performance of bulk and two-dimensional Mg₃Bi₂.The results indicate that dimensional reduction promotes band flattening, significantly increases the density of states, and enhances charge localization, thereby achieving a substantial increase in the Seebeck coefficient. Meanwhile, the increased lattice anharmonicity and reduced phonon group velocity result in a significant decrease in lattice thermal conductivity. At 700 K, the maximum ZT value reaches 3.22, which are notably higher than bulk Mg₃Bi₂. Furthermore, the (1-10) X-direction exhibits excellent mechanical flexibility and plasticity. This study verifies that constructing two-dimensional structures with different crystal planes and layer thicknesses can effectively modulate the thermoelectric properties and mechanical plasticity of bulk Mg₃Bi₂. It provides theoretical support and optimization pathways for its applications in the flexible thermoelectric devices.