Phonon anharmonicity of thermoelectric material HfTe 5 studied by Raman spectroscopy

The understanding of phonon–phonon anharmonic effect in HfTe 5 is essential not only for fundamental scientific interest but also for its potential thermoelectric applications. Here, rectangular ribbon‐shaped HfTe 5 single crystals have been grown. Raman spectroscopy is further utilized to investigate the phonon anharmonicity of HfTe 5 by quantifying the temperature dependence of the phonon mode softening and broadening. We focus on the temperature range from 80 up to 400 K since obvious surface oxidation occurs at higher temperatures. It is found that four phonon anharmonic effects are non‐negligible. The phonon lifetime is greatly reduced by the enhancement of phonon scattering, resulting in the low thermal conductivity in HfTe 5 single crystals.