Search for: All records

Clathrates have been reported to form in a variety of different structure types; however, inorganic clathrate-I materials with a low-cation concentration have yet to be investigated. Furthermore, tin-based compositions have been much less investigated as compared to silicon or germanium analogs. We report the temperature-dependent structural and thermal properties of single-crystal Eu 2 Ga 11 Sn 35 revealing the effect of structure and composition on the thermal properties of this low-cation clathrate-I material. Specifically, low-temperature heat capacity, thermal conductivity, and synchrotron single-crystal x-ray diffraction reveal a departure from Debye-like behavior, a glass-like phonon mean-free path for this crystalline material, and a relatively large Grüneisen parameter due to the dominance of low-frequency Einstein modes. Our analyses indicate thermal properties that are a direct result of the structure and composition of this clathrate-I material. 

High occupancy of cation sites is typical for clathrate-I compositions allowing limited tunability of the electrical properties beyond doping and elemental substitution. Herein, we report on the structure and electrical transport of single-crystal Eu 2 Ga 11 Sn 35 , the sole example of a very low (25%) cation concentration clathrate-I material with atypical transport directly attributable to the structure and stoichiometry. 

Abstract We conducted shock wave experiments on iron carbide Fe₃C up to a Hugoniot pressure of 245 GPa. The correlation between the particle velocity (u_p) and shock wave velocity (u_s) can be fitted into a linear relationship,u_s= 4.627(±0.073) + 1.614(±0.028)u_p. The density‐pressure relationship is consistent with a single‐phase compression without decomposition. The inference is further supported by the comparison of the observed Hugoniot density with the calculated Hugoniot curves of possible decomposition products. The new Hugoniot data combined with the reported 300‐K isothermal compression data yielded a Grüneisen parameter ofγ= 2.23(7.982/ρ)^0.29. The thermal equation of state of Fe₃C is further used to calculate the density profile of Fe₃C along the Earth's adiabatic geotherm. The density of Fe₃C was found to be too low (by ~5%) to match the observed density in the Earth's inner core, and Fe₃C is unlikely a dominant component of the inner core.