The heat capacity of single-crystalline samples of Sr 8Ga 16Ge 30 (SGG) and Ba 8Ga 16Ge 30 (BGG) clathrates was measured to investigate the anharmonicity of the encapsulated atoms. At low temperatures, BGG can be well described by a standard Debye model, and the C p/T 3 versus T plot can be fitted with two Einstein temperatures: θ E1 = 42 K and θ E2 = 74 K. On the other hand, SGG shows deviation from the Debye model. Moreover, neither the Einstein model nor the soft potential model (SPM) alone can fit the peak in the C p/T 3 versus T plot, and the peak should be fitted by employing both models. Our results indicate that the effective electron mass is enhanced by the anharmonic phonons.
- heat capacity
- soft potential model
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry