Study on the thermoelectric properties of p-type doped CsCdF3 and CsHgF3 with quartic anharmonicity

The cubic perovskite materials CsCdF3 and CsHgF3 have extremely low lattice thermal conductivity, but due to the limitations of the previous calculation methods. The CsHgF3 have been considered unstable for a long time. Through self-consistent phonon theory and compressed sensing technology, we verified the stability of CsHgF3, and studied the thermoelectric transport characteristics of p-type doped CsCdF3 and CsHgF3 based on the first principles calculations combined with the Boltzmann transport equation. In addition, we also discussed the influence of the quartic anharmonicity on the lattice dynamics and thermal transport properties of CsHgF3. The results show that the halogen elements in CsHgF3 have strong quartic anharmonicity and directly affect the stability of the material. The lattice thermal conductivity of CsCdF3 and CsHgF3 calculated by self-consistent phonon theory are 2.03 W/mK and 1.23 W/mK at 300 K, respectively, which are higher than the results obtained by the traditional method, but still lower than most existing classical thermoelectric materials. By combining the obtained thermoelectric coefficients, the calculated thermoelectric figure of merit can reach 0.799 and 1.275 for CsCdF3 and CsHgF3 at 700 K, which shows that CsCdF3 and CsHgF3 have potential development prospects in high-temperature thermoelectric application field.