Zheng Li-Rong

The Phase Transition of Eu2O3 under High Pressures

Pressure-induced phase transition of cubic Eu2O3 is studied by angle-dispersive x-ray diffraction (ADXD) up to 42.3 GPa at room temperature. A structural transformation from a cubic phase to a hexagonal phase is observed, which starts at 5.0 GPa and finishes at about 13.1 GPa. The phase transition leads to a volume collapse of 9.0% at 8.6 GPa. The hexagonal phase of Eu2O3 maintains stable up to the highest experiment pressure. After release of pressure, the high-pressure phase transforms to a monoclinic phase. The pressure-volume data are fitted with the Birch-Murnaghan equation of state. The bulk moduli obtained upon compression from the fitting are 145(2) GPa and 151(6) GPa for the cubic and hexagonal phases, respectively, when their first pressure derivatives are fixed at 4.

Multiple conduction behavior of BaRuO3 thin film prepared by pulsed laser ablation deposition

Abstract In this paper, thin films of BaRuO 3 prepared on a Si substrate by the pulsed laser ablation deposition method under oxygen ambient have been studied by means of X-ray diffraction, emission spectroscopy, Rutherford backscattering spectroscopy, RT Hall measurement and resistivity measurement. It is interesting to find that BaRuO 3 thin films, having a different thermal history examined in the same temperature range, show different conduction types including metallicity, semiconduction and semiconductor-metal transition. The explanation about the findings are given using a suggested modified energy band diagram. It is believed that the versatile electrical behavior is helpful for the use in electrical contact materials.

A new cell for X-ray absorption spectroscopy study under high pressure

X-ray absorption fine structure (XAFS) spectroscopy is a powerful technique for the investigation of the local environment around selected atoms in condensed matter. XAFS under pressure is an important method for the synchrotron source. We design a cell for a high pressure XAFS experiment. Sintered boron carbide is used as the anvils of this high pressure cell in order to obtain a full XAFS spectrum free from diffraction peaks. In addition, a hydraulic pump was adopted to make in-suit pressure modulation. High quality XAFS spectra of ZrH2 under high pressure (up to 13 GPa) were obtained by this cell.

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.