压电驱动金刚石对顶砧加压装置的研制和应用

金刚石对顶砧加压装置广泛用于物理、化学、材料等许多科学领域。自Bridgman发明金属对顶砧及随后发展金刚石对顶砧以来,对顶砧装置设计和加压技术得到不断发展。文章介绍采用压电驱动金刚石对顶砧来产生高压,实现低温20 K下原位连续加压,连续加压范围约2—4 GPa。该加压装置具有体积小、操作方便,可装在小型低温恒温器中使用等优点。     

复合型多晶金刚石末级压砧的制备并标定六面顶压机6-8型压腔压力至35GPa

通过分析二级6-8型大腔体静高压装置八面体压腔的受力状况, 研制了一种使用成本低、尺寸大且易于加工的多晶金刚石-硬质合金复合二级(末级)顶锤(压砧). 采用原位电阻测量观测Zr在高压下相变(α-ω, 7.96 GPa; ω-β, 34.5 GPa)的方法, 标定了由多晶金刚石-硬质合金复合末级压砧构建的5.5/1.5(传压介质边长/二级顶锤锤面边长, 单位: mm)组装的腔体压力. 实验表明, 自行研制的多晶金刚石-硬质合金复合末级压砧可使基于国产六面顶压机构架的二级加压系统的压力产生上限从约20 GPa提高到35 GPa以上, 拓展了国内大腔体静高压技术的压力产生范围. 应用这一技术, 我们期望经过末级压砧材料与压腔设计的进一步优化, 在基于国产六面顶压机的二级6-8 型大腔体静高压装置压腔中产生超过50 GPa的高压. 关键词： 二级6-8型大腔体静高压装置 多晶金刚石-硬质合金复合末级压砧 压力标定     

基于金刚石对顶砧的液体高压黏度测量北大核心CSCD

研制了一种基于金刚石对顶砧的液体高压黏度测量装置。该装置由金刚石对顶砧、显微镜和CCD探测器构成,利用红宝石荧光标定压力,通过落球法可简单方便地实现不同压力下液体黏度的测量。利用该装置,测量了高压下丙三醇的黏度,测量结果与已发表的实验数据吻合得很好,验证了测量装置的可靠性。     

基于金刚石对顶砧的液体高压黏度测量

研制了一种基于金刚石对顶砧的液体高压黏度测量装置。该装置由金刚石对顶砧、显微镜和CCD探测器构成,利用红宝石荧光标定压力,通过落球法可简单方便地实现不同压力下液体黏度的测量。利用该装置,测量了高压下丙三醇的黏度,测量结果与已发表的实验数据吻合得很好,验证了测量装置的可靠性。     

低温下使用的金刚石对顶砧高压盒和显微光谱系统

自Bridgeman发明套筒活塞高压装置以来,特别是引入金刚石压砧后,高压物理学发展迅速。这种金刚石对顶砧压力盒,简称为DAC,为研究高压下材料的光学性质提供了极大的方便。为进行高压低温研究,目前国内都是将压机浸入液氮中,或向DAC喷浇液氮。这样只能在77K恒温,且必须取出压机后才能加压。     

毫秒时间分辨同步辐射X射线衍射和高压快速加载装置及应用

高压非平衡相变动力学过程依赖于温度、压强及加载速率,这要求在不同时间尺度内实现快速加载/卸载并进行快速数据采集.本文着重介绍了最近在上海同步辐射光源BL15U1线站设计和发展的时间分辨X射线衍射和快速动态加载金刚石对顶砧(dDAC)实验装置的最新进展.dDAC采用气膜驱动和压电陶瓷驱动两种快速加载方式,在毫秒尺度内实现DAC样品腔压强从常压加压到300 GPa(20μm金刚石台面)以上,并获得了毫秒尺度的时间分辨衍射数据.其中压电陶瓷驱动的d DAC采用新设计的单、双筒驱动方式,具有加载压力大、压缩速率高等特点,加载速率可达13 TPa/s.在快速加压过程中,可同时连续采集X射线衍射谱.探测器采用Pilatus 3X 900 K,帧频达500 Hz,实现了2 ms时间分辨的X射线衍射测量.毫秒时间分辨的X射线衍射和高压快速加载装置丰富了BL15U1线站的高压研究技术,拓展了线站开展超高压实验、非平衡相变动力学等科学研究的能力.     

基于集成技术的金刚石对顶砧原位电学量测量

 金刚石对顶砧是应用最多的高压装置,能够产生超过400 GPa的超高压力,借助激光加温,还可以加载6 000 K的高温。近20年来,基于金刚石对顶砧的微小测量电路集成技术的突破,带动了高压原位电学量测量技术的发展,使常压下能够测量的电学量大部分都能在金刚石对顶砧中的高压环境下实现。全面回顾了基于集成技术的金刚石对顶砧高压原位电学量测量技术的发展历程,介绍了最新的技术进展。     

高温高压下干酪根在水中变化的拉曼光谱原位分析

金刚石作为顶砧 ,通过顶砧压腔装置对干酪根在水中的变化进行拉曼光谱的原位分析 ,压力采用常温常压下石英 4 6 4cm-1的拉曼峰确定。在 2 4 0℃之前 ,可得到水、干酪根以及石英清晰的拉曼峰 ,之后 ,由于金刚石的荧光效应 ,使拉曼信号消失。实验中发现 ,温度从最高温度 4 40℃降到 2 4 0℃ ,拉曼光谱图显示干酪根降解生成了有机小分子     

0.1~3 000 MPa下碳化硅顶砧拉曼光谱作为压力计的研究

 利用Mao-Bell型水热金刚石压腔，以6H型碳化硅晶体作为顶砧，在常温下对碳化硅顶砧的不同点位进行拉曼光谱的原位测量，探讨了在一定条件下利用碳化硅顶砧的969拉曼峰位移作为压力标定的可行性、所具有的优点及需要改进的方面，并且得到了室温下的压力测量公式。     

金刚石对顶砧高压显微光谱系统

一、引 言 金刚石对顶砧高压装置是高压下光学研究的一个有力工具.参照B.Welber等人的装置,我们组装了一套金刚石对顶砧高压显微光谱系统,该系统可用于高压下的吸收和发射光谱测量.由最初的几个实验结果来看,它的性能是可靠的.例如,我们利用该系统测量了非晶态As2S3薄膜样品在0     

Pressure-Induced Shifts of R, R', and B Line-Groups and Ground-State Zero-Field-Splitting of Ruby

By means of improved ligand-field theory, the “pure electronic” presure-induced shifts (PS's) and the PS's due to electron-phonon interaction (EPI) of the R₁, R₂, B₁, B₂, B₃, and R'₃ lines and the ground-state zero-field-splitting of ruby have been uniformly calculated. The calculation results are in very good agreement with all the experimental data. At normal pressure, ruby is a crystal with very strong crystal field. Thus, the admixture of |t₂²(³T₁)e⁴T₂〉and |t³₂²E〉bases in the wavefunction of R₁ level of ruby is small at normal pressure, and it gradually decreases with increasing pressure, which causes the R₁-line PS of ruby to monotonously red shift with approximate linearity. The combined effect of the pure electronic PS of R₁ line and the PS of R₁ line due to EPI gives rise to the total PS of R₁ line. The analyses and comparisons among the features of R₁-line PS's of three laser crystals (ruby, GSGG:Cr³⁺ and GGG:Cr³⁺) have been made, and the origin of their difference has been revealed.     

采用光谱技术研究[C4mim][BF4]的传压和测压性能

金刚石压腔是一种在实验室被频繁使用的高压产生装置,它在高压领域占据着重要地位。当金刚石压腔内传压介质只能提供非静水压环境时,利用传统的红宝石荧光光谱测压方法将很难准确测量样品压强,这也是目前超高压实验面临的普遍困难。若有一种兼具“传压”和“测压”双重功能的物质,根据“相邻位置、相近压强”原则,将能够解决在非静水压环境中测不准样品压强问题。显然,探寻兼具“传压”和“测压”双重功能的物质是一项非常重要的工作。本文将红宝石微粒与离子液体[C₄mim][BF₄]装入金刚石压腔,然后利用金刚石压腔压缩[C₄mim][BF₄]使其提供高压环境,同时采集红宝石的荧光光谱及其附近[C₄mim][BF₄]的拉曼光谱。通过分析红宝石特征荧光峰R₁的峰位,得到了[C₄mim][BF₄]在加压过程中提供的一系列高压环境的压强值。通过分析红宝石特征荧光峰R₁的峰宽,发现[C₄mim][BF₄]在0~6.26和6.26~21.43 GPa两个压强范围内可分别提供静水压环境和准静水压环境,表明[C₄mim][BF₄]在0~21.43 GPa范围内可以作为传压介质使用。此外,还发现[C₄mim][BF₄]在0~2.28,2.28~6.26,6.26~14.39和14.39~21.43 GPa四个压强范围内分别为“液相Ⅰ”、“液相Ⅱ”、“非晶相Ⅰ”和“非晶相Ⅱ”。通过分析[C₄mim][BF₄]中特征拉曼峰ν_(B-F)和ν_(ring)的峰位,发现在[C₄mim][BF₄]四个相态内ν_(B-F)和ν_(ring)的峰位随压强增加均满足线性变化关系,并给出了相应的压强与峰位关系函数,这些函数是[C₄mim][BF₄]用作压标物质的重要依据。综上所述,[C₄mim][BF₄]不仅具有“传压”功能,同时还具有“测压”功能,可同时用作“传压介质”和“压标物质”。研究结果为在非静水压环境中准确测量样品压强提供了重要依据,也为超高压条件下样品压强测量不准确问题提供了新的解决思路。     

Improved Ligand-Field Theory with Effect of Electron-Phonon Interaction

Traditional ligand-field theory has to be improved by taking into account both “pure electronic” contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R₁, R₂, R₃', R₂', and R₁' lines, U band, ground-state zero-field-splitting (GSZFS), and ground-state g factors of ruby and/or GSGG:Cr³⁺ as well as thermal shifts of GSZFS, R₁ line and R₂ line of ruby have been calculated. The results are in very good agreement with the experimental data. Moreover, it is found that the value of cubic-field parameter given by traditional ligand-field theory is inappropriately large. For thermal shifts of GSZFS, R₁ line and R₂ line of ruby, several conclusions have also been obtained.     

Energy Spectrum of YAG:Cr3+ and Thermal Shifts of Its R Lines

Traditional ligand-field theory has to be improved by taking into account both “pure electronic” contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R₁, R₂, R'₃, R'₂, and R'₁ lines, U band, ground-state zero-field-splitting (GSZFS) and ground-state g factors as well as thermal shifts of R₁ line and R₂ line of YAG:Cr³⁺ have been calculated. The results are in very good agreement with the experimental data. In contrast with ruby, the octahedron of ligand oxygen ions surrounding the central Cr³⁺ ion in YAG:Cr³⁺ is compressed along the [111] direction. Thus, for YAG:Cr³⁺ and ruby, the splitting of t₂³⁴A₂ (or t₂³²E) has opposite order, and the trigonal-field parameters of the two crystals have opposite signs. In thermal shifts of R₁ and R₂ lines of YAG:Cr³⁺, the temperature-dependent contributions due to EPI are dominant.     

Energy Spectra of the Tunable Laser Crystal Gd3Ga5O12:Cr3+ and Their Pressure-Induced Shifts

By means of both the theory for pressure-induced shifts (PS) of energy spectra and the theory for shifts of energy spectra due to electron-phonon interaction (EPI), at 300 K, the `pure electronic' contributions and the contributions from EPI to R₁ line, R₂ line, and U band of GGG:Cr³⁺ as well as their PS have been calculated, respectively. The total calculated results are in good agreement with all the experimental data. Their physical origins have been explained. It is found that the mixing-degree of |t₂²(³T₁)e ⁴T₂> and |t₂³²E> base-wavefunctions in the wavefunctions of R₁ level of GGG:Cr³⁺ is considerable under normal pressure, and the mixing-degree rapidly decreases with increasing pressure. The change of the mixing-degree with pressure plays a key role for PS of R₁ line or R₂ line. At 300 K, both the temperature-independent contribution to R₁ line (or R₂ line or U band) from EPI and the temperature-dependent one are important. The remarkable difference between pressure-dependent behaviors of PS of R₁ lines of GGG:Cr³⁺ and GSGG:Cr³⁺ results from the differences of their microscopic properties. The features of emission spectra of GGG:Cr³⁺ at various pressures have satisfactorily been explained.     

基于拉曼频移的白宝石压腔无压标系统高温高压实验标定

在高压实验科学中, 各类宝石压腔是最为常见的高压设备之一, 其样品腔中压力的精确标定是实验的关键. 目前, 人们主要通过加入红宝石等压标物质来进行定压, 但压标物质的加入会增加实验的装样难度, 改变样品腔中的物理化学环境, 甚至直接与实验样品发生反应, 从而对实验结果产生影响. 在0–6.3 GPa和300–573 K下, 利用共聚焦拉曼显微镜, 根据白宝石压砧砧面的ν₁₂ 拉曼频移与温度和压力的变化关系, 建立了一套适用于高温高压水热体系的无压标白宝石压腔系统. 实验结果表明: 白宝石砧面的ν₁₂ 峰随着压力的升高发生线性蓝移, 而随着温度升高则发生线性红移, 且温度和压力对拉曼频移的影响存在耦合效应. 利用本实验结果, 可在高温高压下根据白宝石砧面的拉曼频移计算出样品腔的压力P=(Δλ-0.01913×ΔT)/(1.9158-0.00105×ΔT), 在物理学、材料学和地球科学等领域具有重要应用.     

Photoluminescence of LLGG:Cr crystals under high pressure

We present photoluminescence spectra of La_2.7Lu_2.29Cr_0.01Ga₃O₁₂ and La_2.32Lu_2.59Cr_0.02Ga_3.07O₁₂ doped with Cr³⁺ obtained at high hydrostatic pressure up to 220 kbar, applied in a diamond anvil cell at 20 K and room temperature. In both materials we have obtained a pressure-induced ⁴T₂–²E electronic cross-over. On the basis of the low-temperature R line luminescence at pressures above 100 kbar we have distinguished two dominant Cr³⁺ sites: and β, existing in both materials, and one minor site δ, that exists only in La_2.32Lu_2.59Cr_0.02Ga_3.07O₁₂. The pressure-induced shifts of the R₁, R_1β and R_1δ lines as well as the pressure shift of the broad band related to the ⁴T₂→⁴A₂ transition in both materials have been estimated.     

Magnetic characteristics of R2(Fe, Co)14B systems (R = Y, Nd and Gd)

R₂(Fe, Co)₁₄B compounds (R = Y, Nd and Gd) were prepared in high purity. The magnetic behavior of R₂(Fe, Co)₁₄B compounds is reported over the temperature range 4 to 300 K. The effects of Fe substitution by Co on the saturation magnetization, Curie temperature and anisotropy are presented. The spin-reorientation temperature is lowered as Co replaces Fe. This also results in a reduced cone angle.

The R₂Fe_14−xCo_xB alloys crystallize in the tetragonal structure over the entire concentration range of 0 x 14. When Fe is substituted by Co, the Curie temperature increases significantly, the saturation magnetization increases to a maximum value around x = 2, and the anisotropy becomes planar for R = Y and Gd. The Nd₂(Fe, Co)₁₄B systems all exhibit uniaxial anisotropy at room temperature and Nd₂Co₁₄B is strongly uniaxial at 77 K. The Nd₂(Fe, Co)₁₄B systems are conical at 77 K.     

STRUCTURE AND MAGNETIC PROPERTIES OF NITRIDES R3Fe29-xCrxN4

A systematic investigation of nitrides R₃Fe_29-xCr_xN₄(R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The nitrogen concentration in the nitride R₃Fe_29-xCr_xN_y was determined to be y=4. Nitrogenation leads to a relative volume expansion of about 5.3%. The lattice constants and unit cell volume decrease with in creasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. In average, the increase of Curie temperature upon nitrogenation is about 200 K, compared with its parent compound. The nitrogenation also results in a remarkable improvement in the saturation magnetization and anisotropy fields for R₃Fe_29-xCr_xN₄ at 4.2 K and room temperature, comp ared with their parent compounds. A spin reorientation of Nd₃Fe_24.5 Cr_4.5N₄ occurs at around 368 K, which is 138 K higher than that of Nd₃Fe_24.5Cr_4.5.Magnetohistory effects of R₃Fe_29-xCr_xN₄(R=Nd and Sm) are observed in a low field of 0.04 T. First order magneti zation process occurs in Sm₃Fe_24.0Cr_5.0N₄ in magnetic fields of around 3.0 T at 4.2 K. After nitrogenation the easy magnetization direction of Sm₃Fe_24.0Cr_5.0 is changed from the easy cone structure to the uniaxial. The excellent intrinsic magnetic properties of Sm₃Fe_24.0Cr_5.0N₄ make this compound a hopeful candidate for new high performance permanent magnets.     

FORMATION AND MAGNETIC PROPERTIES OF NEW COMPOUNDS R3Fe29-xCrx(R=Y,Ce,Nd,Sm,Gd,Tb,and Dy)

A systematic investigation of structure and magnetic properties of the new R₃Fe_29-xCr_x compounds(R=Y,Ce,Nd,Sm,Gd, Tb,and Dy)has been performed. The Curie temperature of R₃Fe_29-xCr_x increased with increasing atomic number fromR=Ce to Gd and de creased from Gd to Dy. The saturation magnetization of R₃Fe_29-xCr_x at 4.2 K decreased gradually with increasing atomic number from R=Y to Dy,except for Ce. The spin reorientations of the easy magnetization d irection were observed at around 230 K for Nd₃Fe_24.5Cr_4.5 and 180 K for Tb₃Fe_28.0Cr_1.0,and the magnetohistory effects were obser ved for Nd₃Fe_24.5Cr_4.5 and Sm₃Fe_24.0Cr_5.0 in a low field of about 0.04 T. First order magnetization process occurs in magnetic field of around 2.3 T at room temperature for Tb₃Fe_28.0Cr_1.0. The saturation magnetization of Y₃Fe_27.2Cr_1.8 at 4.2 K is 52.2μ_B/f.u., which corresponds to an average magnetic moment of 1.92μ_B per each Fe atom.