No abstract

A complete set of low temperature elastic constants C ij and piezoelectric coefficients e ij of ␣-quartz single crystal has been investigated by resonance ultrasound spectroscopy coupled with a laser-Doppler interferometry. Most elastic constants showed monotonic elastic stiffening, while C 66 continuously softened as the temperature decreased. Two piezoelectric coefficients e ij showed monotonic decreasing upon cooling, and we found a strong correlation between e 11 and C 66 , representing that thermal contraction induced internal strain plays an important role in their temperature behaviors. Group theoretical lattice dynamics analysis revealed that the elastic softening and the correlation can be attributed to an optical-mode-phonon-type internal strain having doubly degenerated E symmetry in the point group of D 3 .

Articles you may be interested inProducing metastable nanophase with sharp interface by means of focused ion beam irradiation J. Appl. Phys. 105, 044305 (2009); 10.1063/1.3079508 Focused ion beam induced synthesis of a porous antimony nanowire network Crystallographic features of oriented nanocrystals induced by focused-ion-beam irradiation of an amorphous alloy

Thermal conductivity ͑͒ and Seebeck coefficient ͑␣͒ of electron-doped light-metal oxide 12CaO· 7Al 2 O 3 ͑C12A7 electride͒ with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations ͑N e ͒. The semiconducting C12A7 electride exhibits n-type conduction with the highest ␣ value of −100 V K −1 at 300 K. The exhibits an amorphouslike T 2 dependence at low temperatures and varies between 2.3 and 4.5 Wm −1 K −1 at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO ͑15 Wm −1 K −1 ͒ and Al 2 O 3 ͑30 Wm −1 K −1 ͒. These properties are attributed to the cage structure, suggesting that the semiconducting electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of electrides evaluated by a dimensionless figure of merit ͑ZT͒ shows an optimized value of 2 ϫ 10 −3 at 300 K for the semiconducting electride with N e of 5 ϫ 10 20 cm −3 .

A molecular dynamics simulation was performed to investigate the structural changes during a shear deformation process in an amorphous metal. An amorphous model is constructed from Ni atoms interacting via a Morse-type pairwise additive potential. At shear stresses below 2.4 GPa, shear strain increased linearly with increasing shear stress. However, large shear deformation occurred when shear stress reached 2.8 GPa. During this shear deformation, crystallization was observed in the model. The crystalline phase had an fcc structure which had an orientation relationship, i.e., the shear direction and a (111) plane are parallel. This relationship was consistent with our experimental study on a Ni–P amorphous alloy.