Phase transition in layered perovskite-like manganate Ca3Mn2O7 under high pressure

In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.     

大功率全钒液流储能电池的研究

电力的供应紧张已成为制约我国国民经济稳定、可持续发展的瓶颈.电力系统对大规模储能技术提出了现实需求.同时,基于可再生能源发电的分布式供能技术将成为我国能源领域的发展重点.可再生能源(如风能、太阳能等)发电具有不稳定和不连续的间歇性特点,需要开发和建设配套的储能电池来保证发电和供电的连续和平稳.     

高压及热处理对氮碳薄膜激光诱导荧光效率的影响

 应用激光激发荧光光谱实验对经热处理后及高压条件下的氮碳薄膜荧光光谱进行了测量分析。实验显示,热处理效应和高压效应均导致薄膜荧光效率降低,前者表现为不可恢复,后者为可恢复即卸压后荧光效率的恢复,表明导致荧光光谱效率降低的微观机制不同,为氮碳薄膜荧光模型提供了新的实验证据。     

Isostructural Phase Transition of TiN under High Pressure

In situ high-pressure energy dispersive x-ray diffraction experiments on polycrystalline powder TiN with NaCltype structure have been conducted with the pressure up to 30.1 GPa by using a diamond anvil cell instrument with synchrotron radiation at room temperature. The experimental results suggest that an isostructural phase transition might exist at about 7 GPa as revealed by the discontinuity of V/Vo with pressure.     

钙钛矿型(Pbnm)化合物在高压下的结构变化

ABX₃型钙钛矿,最常见的结构为斜方晶系Pbnm,在高压下的结构变化具有多样性.本文简要介绍了3个参量(t,V_A/V_B,E_tot),描述ABX₃型钙钛矿结构的稳定性,全面总结了应用这3个参量建立的高压下钙钛矿结构(Pbnm)变化模型,基中有些模型对所有的钙钛矿结构都适合.通过举例,运用不同的模型对CaTiO₃(Pbnm)在高压下的结构变化进行综合分析,定性地得出随着压力的增加其结构的对称性应降低.     

BeO的高压能量色散X射线衍射研究

在北京同步辐射高压站进行了BeO高压原位能量色散X射线衍射实验. 在从常压下加压至42GPa的过程中,BeO保持常压的六方纤锌矿结构(Wurtzite),没有发生相变,晶胞体积随着压力增加单调减小.用Murnaghan方程拟合出BeO在0.6—42.0GPa范围内的P-V状态方程,得到体弹模量K₀=276GPa.     

Compression Behaviour and Equation of State of Zr44.4Nb7Cu13.5Ni10.9Be24.3 Bulk Metallic Glass up to 39 GPa

The compression of Zr44.4Nb7Cu13.5Ni10.8Be24.3 bulk metallic glass (BMG) is investigated at room temperature up to 39 GPa using in situ high-pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state of the BMG is obtained by the calculation of the radial distribution function. Pressureinduced structural relaxation is exhibited. It is found that below about 6 GPa, the existence of excess free volume contributes to the rapid structural relaxation, which gives rise to rapid volumetric change, and the structural relaxation results in structural stiffness under higher pressure.     

Growth of bulk single crystals β-FeSi2 by chemical vapour deposition

Bulk single crystals β-FeSi2, as a new photoelectric and thermoelectric material, has been successfully grown using chemical vapor transport techniqueby using iodine as transport agent in a sealed ampoule. The effects of crystal growth condition on quality and morphologies of the single crystals were studied. Both needle-like and grain-like single crystals were gained. By changing substrate temperature, tetrahedral high quality α-FeSi2 single crystals were also obtained.     

高压下的同步辐射能量色散粉末衍射

 同步辐射已经成为高压研究的一个非常理想的光源。在北京同步辐射装置（BSRF）上、结合金刚石对顶砧超高压实验技术建立起来的能量色散X射线粉末衍射系统,已用于物质状态方程和结构相变的研究。介绍了能量色散衍射方法,以及同步辐射原位测试过程。     

Compression behavior and phase transition of β-Si_3N_4 under high pressure

The compressibility and pressure-induced phase transition of β-Si_3N_4 were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the x-ray powder diffraction data verified that the hexagonal structure(with space group P63/m, Z = 2 formulas per unit cell) β-Si_3N_4 remained stable under high pressure up to 37 GPa. Upon increasing pressure, β-Si3 N4 transformed to δ-Si_3N_4 at about 41 GPa. The initial β-Si_3N_4 was recovered as the pressure was released to ambient pressure, implying that the observed pressureinduced phase transformation was reversible. The pressure–volume data of β-Si_3N_4 was fitted by the third-order Birch–Murnaghan equation of state, which yielded a bulk modulus K_0= 273(2) GPa with its pressure derivative K_0= 4(fixed)and K0= 278(2) GPa with K 0= 5. Furthermore, the compressibility of the unit cell axes(a and c-axes) for the β-Si_3N_4 demonstrated an anisotropic property with increasing pressure.