Quasi-layered Crystal Structure Coupled with Point Defects Leading to Ultralow Lattice Thermal Conductivity in n-Type Cu2.83Bi10Se16

Cu 2.83 Bi 10 Se 16, a new n-type thermoelectric material, was synthesized via a high-temperature solid-state routine. The quasi-layered structure features of Cu 2.83 Bi 10 Se 16 were established by a comprehensive study including variable-temperature single-crystal X-ray diffraction, synchrotron powder X-ray diffraction, DFT calculations, and resonant ultrasound spectroscopy. The structural relationship between Cu 2.83 Bi 10 Se 16 and two previously reported compounds, Cu 1.6 Bi 4.8 Se 8 and Cu 1.78 Bi 4.73 Se 8, is addressed. The quasi-layered structure of Cu 2.83 Bi 10 Se 16 coupled with point defects accounts for its ultralow lattice thermal conductivity. First-principles simulations predict that the electrical properties of Cu 2.83 Bi 10 Se 16 are sensitive to Cu content, which is confirmed by the thermoelectric property measurements of Cu 2.83– x Bi 10 Se 16 ( x = 0, 0.1, and 0.2) samples. Through tuning the Cu content, Cu 2.73 Bi 10 Se 16 shows the best performance due to the highest Seebeck coefficient combined with a moderate electrical conductivity, achieving zT = 0.42 at 775 K. This work proves that crystal structure engineering can achieve extremely low lattice thermal conductivity in crystalline solids.