High Bulk Modulus of Nanocrystal γ-Fe2O3 with Chemical Dodecyl Benzene Sulfonic Decoration Under High Pressure

Structural transformation in γ-Fe2O3 nanocrystals (about 1Onm) with dodecyl benzene sulfonic (DBS) coated is studied by using high-pressure energy dispersive x-ray diffraction of synchrotron radiation and high-resolution transmission electron microscopy (HRTEM). Relative to the bulk crystal, the transition pressure showed a decrease while the compressibility increases significantly up to 375 (±9 GPa). HRTEM picture confirmed that there is surface cladding surrounding nanocrystals due to DBS, which formed new special boundaries between nanocrystals and should be different from the ordinary grain boundaries. The experimental results imply that the surface layers of γ-Fe2O3 nanocrystals have strong effect on the compressibility.

Measurement of R Line Fluorescence in Ruby Using the Diamond Anvil Cell at Low Temperature

Using our custom-built high-pressure cryostat we have performed the measurements of the R line fluorescence of ruby in the diamond anvil cell from room temperature down to 90K.The maximum pressure was 11.1 GPa.By computer curve fitting,different equations have been found for functions of wavenumber versus temperature between ambient pressure and 2.7 GPa.The changes of the shape and linewidth of R lines were observed.

Studies on CsBr with Synchrotron Radiation Under Ultrahigh Pressure up to 115GPa

In situ high pressure energy dispersive x-ray diffraction experiments have been carried out on CsBr by using diamond anvil cell device with synchrotron radiation source.The maximum pressure is 115 GPa.The structure of CsBr is changed from simple cubic phase to tetragonal phase at pressure about 53 GPa,marked by the splitting of its strongest diffraction line(110).At pressure above 98GPa,the color change of CsBr from transparent to red-brown was observed.No pressure-induced transition from insulator to metal is found at higher pressure up to 115GPa.

Pressure Induced Phase Transition in TiB

In situ high pressure x-ray diffraction and electrical resistance experiments on TiB have been carried out by using a diamond anvil cell device. The results revealed that the sample undergoes a first-order phase transition at pressures of 3.5-5.0 Gpa and 4.0-5.5 Gpa for the x-ray diffraction and electrical resistance experiments, respectively. The parameters of the state equation are calculated before and after the phase transition and compared with the values calculated by Mohn et al. [J. Phys. C: Solid State Phys. 21(1988)2829] using the augmented spherical wave method.

Raman Study of Nitrogen at High Pressure

Raman spectra of the nitrogen loaded in a diamond anvil cell with the compressed gas have been investigated at the pressure up to 40GPa.Pressure was measured in terms of the ruby fluorescence.The curve of frequency vs pressure was obtained by micro-Raman spectrometer.According to the experimental results,the frequency of two stretching mode peaks increases steadily from 2340 and 2347cm^(-1) at 5.2 GPa to 2396 and 2434 cm^(-1) at 40 GPa,respectively.The interval between two peaks also increases gradually with pressure increasing.A new peak(2402cm^(-1))of the stretching mode was observed near 40 GPa,which may be associated with the distortion of the Pm3n structure or the formation of low-symmetry structure.

Pressure-Induced Amorphous Transition of Li_(2)Ge_(7)O_(15) Crystal

Pressure-induced amorphous transition of Li_(2)Ge_(7)O_(15)(LGO)crystal has been investigated by using in situ high pressure energy dispersive x-ray diffraction with synchrotron radiation at the pressure up to 21.6 GPa.Diamond anvils were used to generate high pressure.Pressure was measured in terms of the diffraction of Pt as an internal pressure standard.The crystal structure of LGO is an orthorhombic lattice at atmospheric pressure.According to the high pressure x-ray diffraction results,new diffraction lines begin to appear and LGO undergoes an intermediate phase transition at the pressure of 12.9 GPa.But,the diffraction lines disappear wholly and LGO becomes an amorphous phase at the pressure of above 14.8 GPa.This amorphous transition is irreversible.

Development of pressure-modulated EXAFS method

Many modulation techniques have been widely applied to improve the quality of conventional spectra. Here a pressure-modulated EXAFS method is proposed to detect the small changes of local structure induced by the modulation of high pressure. In the experiment a dynamic diamond anvil cell was used to put a periodic load on the sample and lock-in amplifier to measure the modulated EXAFS signals. We have applied this technique to ZnSe and revealed a sensitivity to atomic displacement of 0.1 pm that is about ten times better than that of traditional EXAFS.