Lattice Thermal Conductivity for Different Phases of HfO₂: A DFT-Based Study

Recently, Hafnium oxide (HfO 2 ) has attracted significant interest due to its robust nanoscale ferroelectricity and excellent compatibility with CMOS technology, positioning it as a promising candidate for next-generation electronic devices. While considerable research has focused on its ferroelectric properties, the lattice thermal properties of different HfO 2 phases remain insufficiently understood. In this study, the structural characteristics, phonon dispersions, and heat transport behavior of HfO 2 in its monoclinic, orthorhombic, tetragonal, and cubic phases are systematically investigated via first-principles calculations. The monoclinic phase, identified as the ground state, exhibits the highest lattice thermal conductivity of 10.87 W/mK at room temperature, followed by the ferroelectric orthorhombic phase with a conductivity of 6.99 W/mK. Both phases are predominantly governed by particle-like heat transport involving phonons with extended mean free paths reaching up to 3856 nm and 4022 nm, respectively. In contrast, the tetragonal and cubic phases demonstrate extremely low thermal conductivities of 0.12 W/mK and 0.09 W/mK, respectively. These low values arise primarily from their dynamic instability and considerable wave-like heat transport contributions, exceeding 50% at elevated temperatures. Phonon dispersion analyses further indicate imaginary frequencies in the tetragonal and cubic phases, consistent with their experimental stability only at higher temperatures. Additionally, strong coupling between acoustic and optical phonons in all phases significantly enhances phonon-phonon scattering, thereby reducing lattice thermal conductivity. These findings provide a comprehensive understanding of phase-dependent heat transport mechanisms in HfO 2 , highlighting the interplay between particle-like and wave-like processes and offering valuable guidance for optimizing nanoscale thermal management and electronic device design.