Das erste Erdalkalimetall-Argentato-Mercurat(II): BaAg2Hg2O4

Summary BaAg₂Hg₂O₄ was prepared by an oxygen high-pressure technique. Single crystal X-ray investigations led to tetragonal symmetry, space group D _4h ³ – P4/nbm;a=6.793;c=7.086 Å;Z=2. Hg²⁺ and Ag⁺ show dumb-bell like coordination by oxygen whereas Ba²⁺ ions are surrounded by 8 O^2– forming distorted cubes. The BaO₈-polyhedra distortions are discussed in respect to the incorporation of Hg²⁺ ions into the BaAg₂O ₄ ^2– network.

     

Pr3Mo4B6O24(OH)3: High-Pressure/High-Temperature Synthesis of an Acentric Rare Earth Molybdenum Borate

We report on the synthesis of a new praseodymium molybdenum borate under high-pressure/high-temperature conditions. The new compound with the sum formula Pr₃Mo₄B₆O₂₄(OH)₃ crystallizes acentrically in the monoclinic space group Cm displaying a new structure type. The structure was solved via single-crystal structure determination. Additionally, the proposed structural model was confirmed by powder X-ray diffraction, second harmonic generation measurement, and single-crystal infrared and Raman spectroscopic investigation.     

高压下铌酸锌钶铁矿结构相变的原位拉曼光谱和X射线衍射研究

通过原位高压拉曼光谱和X射线衍射对ZnNb₂O₆晶体在29 GPa以下的结构转变进行了研究.拉曼光谱显示, 多数拉曼峰强度减弱, 且随着压力增加向高波数方向移动.压力频移曲线分别在10, 16 和20 GPa处形成了拐点.原位X射线衍射谱在10.6 GPa以上有旧峰消失和新峰出现.结果分析表明, ZnNb₂O₆钶铁矿结构压缩过程中发生了一个可逆压致相变, 此相变从10 GPa左右开始, 到16 GPa左右完成, 继续增加压力到20 GPa以上则形成无序状态.     

The case for universality of the phase diagram of the Fabre and Bechgaard salts

We report the observation of superconductivity in the spin-Peierls Fabre salt (TMTTF)₂PF₆ from pressure dependent electrical transport measurements above a threshold of 4.35 GPa. The data complete the sequence of ground states of this compound in the temperature and pressure plane adducing an empirical basis to the universal character of the phase diagram of the Fabre salts and their selenide analogues, the Bechgaard salts. The structure of the phase diagram at the approach of the crossover between spin-density wave and superconducting states is compared with the results of scaling theory of the interplay between both electronic instabilities under pressure. The comparison supports the view that magnetism and superconductivity in these compounds have a common electronic origin. Received 10 January 2001     

金红石高温高压相变的Raman光谱特征

以Ar作压力介质,在准静水压力条件下,利用激光加热DAC技术和显微Raman光谱原位测试技术,在0～35 GPa压力范围开展金红石的高温高压相变研究。在室温条件下,金红石结构TiO₂于13.4 GPa开始转变成斜锆石相,于21 GPa时转变完全,并直到35 GPa时斜锆石相稳定存在。在压力分别为29.4和35.0 GPa时,用YAG激光器发出的波长为1.064 μm的红外激光束扫描加热样品,TiO₂斜锆石高压相转变成另一Pbca结构高压相。卸压时,Pbca相于26.3 GPa时转变成斜锆石相。斜锆石相转变成Pbca相需要加热才能发生,而卸压时却在较小的压力区间即迅速转变完全,两相转变压力边界在28 GPa左右。进一步卸压,斜锆石相直到11 GPa仍稳定,在7.6 GPa时斜锆石相与α-PbO2相两相共存,5 GPa时完全转变成α-PbO₂相,并直到常压该相以亚稳定态存在。     

静高压下邻苯二甲酸二辛酯增塑双酚A型聚碳酸酯体系中立体开放球晶的生长

通过加入增塑剂邻苯二甲酸二辛酯(DOP), 改变高分子链在压力作用下的运动能力, 培养出具有独特形貌、亚结构为折叠链晶体和三维立体的开放聚合物球晶.     

高温高压密闭消解-ICP-MS测定垃圾焚烧残渣中重金属及稀土元素

采用高温高压密闭消解-电感耦合等离子体质谱(ICP-MS)测定了垃圾焚烧残渣中的Cr, Co, Ni, Cu, Zn, Zr, Cd, Ba和Pb共9种重金属元素及Sc, Y, La, Ce, Pr, Nd等16项稀土元素的含量。实验确定密闭消解罐中,以HF-HNO₃-HCl(1∶2∶1)三元混酸体系于185℃烘箱中12 h可完全消解垃圾焚烧残渣样品,同时对ICP-MS测试工作条件(包括雾室温度、雾化气流速、辅助气流速、冷却气体流速、采样深度等)进行了优化。采用Rh为内标元素进行信号漂移校正和基体补偿,得到25种分析元素标准曲线的线性相关系数(r)大于0.999 9,方法检出限在0.001～1.01 ng·g^-1,样品分析测试的相对标准偏差(RSD)小于4.5%(n=3)。测试结果表明本次分析的垃圾焚烧残渣样品中Cr, Cu, Zn, Zr, Cd, Ba和Pb元素含量偏高,其中Pb含量高达(1 459±8) mg·kg^-1,稀土元素平均总量为(199±2) mg·kg^-1,整体呈下降趋势,并显示相...     

Synthesis of single-crystal perovskite PbCrO3 through a new reaction route at high pressure

As a new member in the family of Mott system, perovskite PbCrO₃ has recently been uncovered to exhibit fantastic structural transition under pressure, coupled with magnetic, electronic, and ferromagnetic transitions, which provide many opportunities for understanding of correlated system. However, it is still challenging to synthesize high-quality single-crystal PbCrO₃, leading to the limited exploration of this Mott compound. In this work, we formulate a new high-pressure reaction route for preparation of high-quality PbCrO₃ crystals between PbCl₂ and Na₂CrO₄ at high pressure of 5–10?GPa and at high temperature of 750–1500°C. Because of the formation of reaction byproduct NaCl, the final product can readily be separated by washing with water. The obtained sample is in the form of single crystal with crystallite size up to 200?μm. In addition, combined with X-ray diffraction measurement, a tentative pressure-temperature synthesis diagram of PbCrO₃ is mapped out from the reaction between PbCl₂ and Na₂CrO₄ and the reaction mechanism is also explored in detail.     

High-pressure synchrotron X-ray diffraction study of tremolite and actinolite in various fluids

Pressure-dependent structural and morphological changes of two amphibole minerals, tremolite and actinolite, were investigated up to 7.0 GPa using synchrotron X-ray powder diffraction underthree different pressure transmission media (PTM): water (W), CO₂ and silicone oil (SI). The elastic response of tremolite and actinolite are found to be dependent on the PTM used. When using water (W) as PTM, tremolite and actinolite show normal volume contractions with bulk moduli of 74(1) and 78(1) GPa, respectively. When using CO₂ as PTM, we observe the formation of calcite from tremolite above 3.8(1) GPa, whereas actinolite did not show any carbonation reaction. Under silicone oil PTM, we observe modulated volume contraction behaviors in both samples, compared to water and CO₂ PTM, with bulk moduli in the order of 90(1) and 94(4) GPa for tremolite and actinolite, respectively.     

High-pressure elasticity of poly(methyl methacrylate) up to 31.5 GPa studied by Brillouin spectroscopy

High-pressure acoustic properties of poly(methyl methacrylate) (PMMA) was investigated up to 31.5 GPa by using a Fabry-Perot interferometer and a diamond anvil cell. Both backscattering and forward, symmetric scattering geometries were used to derive the pressure dependences of the longitudinal sound velocity, the refractive index, and the density over the investigated pressure range. These physical properties showed rapid increases upon compression up to ∼5 GPa, above which they exhibited sluggish increases upon further increase. The crossover behavior at ∼5 GPa was attributed to the change in the densification of PMMA caused by complete collapse of free volume in this polymeric material.