Helical dislocation-driven plasticity and flexible high-performance thermoelectric generator in α-Mg3Bi2 single crystals

Inorganic plastic semiconductors play a crucial role in the realm of flexible electronics. In this study, we present a cost-effective plastic thermoelectric semimetal magnesium bismuthide ( α -Mg 3 Bi 2 ), exhibiting remarkable thermoelectric performance. Bulk single-crystalline α -Mg 3 Bi 2 exhibits considerable plastic deformation at room temperature, allowing for the fabrication of intricate shapes such as the letters “SUSTECH” and a flexible chain. Transmission electron microscopy, time-of-flight neutron diffraction, and chemical bonding theoretic analyses elucidate that the plasticity of α -Mg 3 Bi 2 stems from the helical dislocation-driven interlayer slip, small-sized Mg atoms induced weak interlayer Mg-Bi bonds, and low modulus of intralayer Mg 2 Bi 2 2- networks. Moreover, we achieve a power factor value of up to 26.2 µW cm -1 K -2 along the c-axis at room temperature in an n-type α -Mg 3 Bi 2 crystal. Our out-of-plane flexible thermoelectric generator exhibit a normalized power density of 8.1 μW cm -2 K -2 with a temperature difference of 7.3 K. This high-performance plastic thermoelectric semimetal promises to advance the field of flexible and deformable electronics. The authors find that the plasticity of magnesium bismuthide (α-Mg 3 Bi 2 ) arises from helical dislocation-driven interlayer slip, and the dispersion of lightweight Mg atoms also plays a pivotal role in facilitating strain redistribution during plastic deformation.