The previous works commonly adjust the carrier concentration through acceptor doping, but at the same time, the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu 3 SbSe 4 -based materials. In this work, a microwave-assisted hydrothermal synthesis method was used to synthesize Cu 3 SbSe 4 /TiO 2 hollow microspheres. Part of TiO 2 participates in the reaction, replaces the Sb site of Cu 3 SbSe 4 to form holes, and the rest is dispersed in the matrix in the form of the second phase. The first-principles calculations reveal that the doping of Ti significantly changes the band structure and phonon spectrum, thereby regulating carrier concentration while increasing phonon scattering. In addition, experimental results show that the energy filtering effect generated by the extra-mixed TiO 2 nano particles, which suppresses the decrease of Seebeck coefficient by acceptor doping. Consequently, the highest average power factor 897.5 μW m −1 K −2 and the zT peak value of 0.70 can be obtained in Cu 3 SbSe 4 /6%TiO 2 sample at 298–623 K. This work provides a new sight to improve the thermoelectric properties in Cu 3 SbSe 4 through carrier concentration regulation and nano-phase composition.
While phonon anharmonicity affects lattice thermal conductivity intrinsically and is difficult to be modified, controllable lattice defects routinely function only by scattering phonons extrinsically. Here, through a comprehensive study of crystal structure and lattice dynamics of Zintl-type Sr(Cu,Ag,Zn)Sb thermoelectric compounds using neutron scattering techniques and theoretical simulations, we show that the role of vacancies in suppressing lattice thermal conductivity could extend beyond defect scattering. The vacancies in Sr 2 ZnSb 2 significantly enhance lattice anharmonicity, causing a giant softening and broadening of the entire phonon spectrum and, together with defect scattering, leading to a ~ 86% decrease in the maximum lattice thermal conductivity compared to SrCuSb. We show that this huge lattice change arises from charge density reconstruction, which undermines both interlayer and intralayer atomic bonding strength in the hierarchical structure. These microscopic insights demonstrate a promise of artificially tailoring phonon anharmonicity through lattice defect engineering to manipulate lattice thermal conductivity in the design of energy conversion materials.
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