International audienceA structural peculiarity of the electronic topological transition (ETT) occurring within the pressure stability range of the low-pressure rhombohedral phase I has been evidenced in Bi2Te3. On both sides of the ETT the structure remains unchanged. Nevertheless, precise investigation of x-ray diffraction patterns allows us to conclude that this ETT obeys the lamellar character of this compound but in a counterintuitive way. Indeed, the signature of this ETT can be detected only in the layers' plane in the pressure variation of the lattice parameter a with a 25% increase of the lattice modulus and a 68% decrease of its pressure derivative. On the contrary, no singularity occurs perpendicularly to the layers of the Bi2Te3 structure
Nanocrystalline Bi2Te3 was produced by mechanical alloying and its properties were investigated by differential scanning calorimetry (DSC) x-ray diffraction (XRD), Raman spectroscopy (RS), and photoacoustic spectroscopy (PAS). Combining the XRD and RS results, the volume fraction of the interfacial component in as-milled and annealed samples was estimated. The PAS results suggest that the contribution of the interfacial component to the thermal diffusivity of nanostructured Bi2Te3 is very significant.
International audienceNanometric orthorhombic ZnSb was prepared by mechanical alloying and its structural stability was studied as a function of pressure. The changes were followed by Raman and x-ray absorption spectroscopy. Between 11.0 and 14.6 GPa, we observed an irreversible phase transformation from the orthorhombic phase to a hexagonal hP1 phase. A similar transformation had been previously observed at 7 GPa for bulk ZnSb. The difference in the phase transformation pressures is attributed to an interfacial component of the nanometric structur
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