Thermoelectric properties of Bi_2-xTi_xO₂Se with the shear exfoliation-restacking process

Bi₂O₂Se is a potential medium-temperature n-type thermoelectric material owing to its lower lattice thermal conductivity and larger Seebeck coefficient. However, very low electrical conductivity of pristine polycrystalline Bi₂O₂Se hinders further enhancement of its thermoelectric performance. In this work, the thermoelectric properties of Bi₂O₂Se were investigated by Ti-doping with the shear exfoliation- restacking process. The results show that both the electron content and mobility can be further improved by Ti-doping with the shear exfoliation-restacking process, thus a higher electrical conductivity can be obtained. (e.g., 368 S cm⁻¹ of Bi_1.99Ti_0.01O₂Se at room temperature) On the other hand, the thermal conductivity of Bi_1.99Ti_0.01O₂Se is suppressed to 0.84 Wm⁻¹ K⁻¹ at 772 K. Finally, the ZT peak of Bi_1.99Ti_0.01O₂Se is raised to 0.56, which is 1.2 times of that of un-doped sample. The results show that the thermoelectric properties of Bi₂O₂Se can be further optimized by Ti doping with the shear exfoliation-restacking process.