Structure and Dynamical Properties of Superionic Conductors

1.用<plus-minus>常规的粉末X射线衍射方法确定了473 K时Cu_2Se超离子相的晶体结构为立方晶系，空间群为O^5_-Fm_（3 m），晶格常数α =5.833 ± 0.003。这一结论也得到了反常X射线散射测量的支持.本文用Rietveld方法和X射线粉末衍射数据分析了CuBrSe_3的室温晶体结构。它属于正交晶系，空间群为Pnc 2。CuBrSe_3的结构包括Cu^+离子的有序排列.在100 ~ 523 K温度范围内测定了比热随温度的变化曲线.在230 K、281 K和286 K分别观察到CuBrTe、硫砷铅矿和CulTe_2的新相变。低温比热测量得到的新相与铜原子的有序分布有关.通过对比热-温度曲线的分析，确定了CuBrTe-CuXTe（X=C1和I）体系的相图.用飞行时间法测量了Cu_2Se、CuI、Cu_ Se和Cu_ S的中子非弹性散射<1.8><1.8>。在这些物质中存在着低能量的无磁共振激发，其能量接近 * Ω-3.4 meV，这在铜离子导体中是常见的。

1. The cubic system of the space group denoted by O^5_-Fm3m with the lattice constant of alpha=5.833<plus-minus>0.003 A has been found feasible for the crystal structure of superionic phase of Cu_2Se at 473 K using the usual powder X-ray diffraction method. The conclusion has also been supported by the anomalous X-ray scattering measurement.2. The crystal structure of CuBrSe_3 at room temperature has been analyzed by the Rietveld method with X-ray powder diffraction data. It belongs to the orthorhombic system with the space group Pnc2. The structure of CuBrSe_3 includes the ordered arrangement of Cu^+ ions.3. Specific heat vs temperature curve was measured in the temperature range between 100 K and 523 K. New phase transitions in CuBrTe, CuITe and CulTe_2 were observed at 230 K, 281 K and 286 K, respectively. The new phases obtained by the present specific heat measurement at low temperature would be related to an ordered distribution of copper atoms.4. Phase diagram of CuBrTe-CuXTe (X=C1 and I) system was determined from the analysis of the specific heat vs temperature curves.5. Neutron inelastic scatterings of Cu_2Se, CuI, Cu_<1.8>Se and Cu_<1.8>S were measured by the time-of-flight method at room temperature. Low-lying despersionless excitations near *omega - 3.4 meV, which would be common to copper ion conductors, existed in these substances.