Abstract: Two-dimensional layered CuInP₂Se₆ crystals have attracted extensive attention owing to its ferroelectricity and various unique optical properties. However, the lack of research on their thermal properties hindered its further application. In this study, dense polycrystalline CuInP₂Se₆ was prepared by vapor transport combined with spark plasma sintering (SPS), and its thermal stability and thermal transport properties were investigated systematically. Thermogravimetric analysis results show that CuInP₂Se₆ does not decompose or undergo phase transitions in the temperature range of 300-740 K. Within the temperature range of 300-623 K, the thermal conductivity decreases from 0.63 W·m^-1·K^-1 to 0.35 W·m^-1·K^-1 parallel to the SPS pressing direction, and from 1.34 W·m^-1·K^-1 to 0.93 W·m^-1·K^-1 perpendicular to the SPS pressing direction. To explore the key factors influencing the thermal conductivity of CuInP₂Se₆, corresponding theoretical calculations and sound velocity measurements were carried out. Results reveal strong phonon scattering inside the material, and CuInP₂Se₆ possesses a low transverse sound velocity (V_T=1199 m·s⁻¹) and strong lattice anharmonicity (γ=1.83). The low thermal conductivity of CuInP₂Se₆ originates from the synergistic effect of strong phonon scattering, low sound velocity, and strong lattice anharmonicity. This study provides theoretic mechanism and experimental data for application of CuIn P₂Se₆.

Key words: two-dimensional layered material, CuInP₂Se₆, thermal transport, low thermal conductivity