90 GPa（准）静水压力的产生及压力分布的测量

 本文使用固态氩做传压介质，在自制的Mao-Bell型金刚石对顶砧装置中获得了90 GPa的准静水压。通过测量样品室内不同位置上红宝石荧光R₁线的频移来确定压力分布。实验结果表明在80 GPa以下，样品室内不同位置上的压力与平均压力（p）的差Δp很小，最大的Δp/p不超过1.5%。在90 GPa时，红宝石的荧光R线与常压的很相似。这表明利用固态氩做传压介质可以获得接近100 GPa的准静水压。此外，对红宝石荧光光谱中位置在14 938 cm^-1和14 431 cm^-1两条谱线随压力的变化情况也作了讨论，并由此得出结论，14 938 cm^-1这条线也可用来标定压力。     

The rhombohedral-cubic transition in the IV-VI semiconductor GeTe under high pressure

Abstract

The IV-VI semiconductor GeTe was studied at room temperature as a function of pressure in a truly hydrostatic medium up to 8 GPa and in a quasi-hydrostatic environment, silicone grease, up to 25 GPa     

126.5 GPa准静水压下的光谱学实验

 本文介绍了作者利用国内加工的金刚石压砧装置及组建的微区光谱系统进行100 GPa（百万大气压）准静水压光谱学实验的概况，证明压力产生装置和微区光谱系统的多功能性是充分可靠的。实验中遇到的压力产生能力超过压力测量能力的事实，反映了高压光谱学实验在压力范围扩大时所遇到的挑战。文中对高压下的拉曼、发射、吸收及反射光谱的实验原理和实验方法也作了概略的介绍。     

Synthetic diamonds for multimegabar pressures in the diamond anvil cell

Abstract

Synthetic Type 1b yellow diamonds containing nitrogen in substitutional form and with extremely low birefringence were used as anvils for ultra high pressures in the diamond anvil cell. Pressures were measured by the ruby fluorescence technique to above 200 GPa. Using x-ray diffraction the maximum pressure was 210 GPa, while an x-ray based pressure of 245 GPa was achieved with natural diamonds with a somewhat more optimal geometry. Nitrogen platelets appear to be not essential for exceeding 200 GPa. The optical properties of synthetic diamond at ambient and megabar stresses will be discussed.     

X-ray studies of the semiconductors snas,InTe, TlS and TISe UP TO 43 GPa

Abstract

The structures of the semiconductors SnAs, InTe, TlS and TlSe have been investigated using high-pressure (HP) diffraction technique-a gasketed diamond anvil cell (DAC)'. The pressure was measured by ruby fluorescence technique. The first order reversible transition from NaCl to CsCl structure was found in SnAs with volume discontinuity 5% the two-phase area extends from 32 to 43 GPa. The volume change V/v,(P) of the SnAs is shown in Figure 1. In agreement with the gomology rule3, the same pressure effect has been found in Sn_xSb1?x atP=9 GPa2.     

Ultrahigh pressure equation of state of tantalum to 310 GPa

ABSTRACT

The isothermal compression of transition metal tantalum (Ta) was studied in a diamond anvil cell by X-ray diffraction utilizing rhenium (Re) and gold (Au) as internal X-ray pressure standards. The Re pressure marker was employed during non-hydrostatic compression to pressures up to 310?GPa while the Au pressure marker was used during quasi-hydrostatic compression in a neon pressure-transmitting medium to 80?GPa. Two ultra-high pressure experiments were conducted on Ta and Re mixtures utilizing focused-ion beam machined toroidal diamond anvils with central flats varying from 8 microns to 16 microns in diameter. The Ta metal was observed to be stable in the body-centered-cubic phase to a volume compression V/V₀?=?0.581. The measured equations of state (EOS) of Ta using two different calibrations of the Re pressure marker are compared with the ambient temperature isotherm derived from shock compression data. We provide a detailed analysis of EOS fit parameters for Ta under quasi-hydrostatic and non-hydrostatic conditions.     

Comparison of the Raman pressure shift and the Raman temperature shift of benzene and diamond with the ruby soale

Abstract

In order to serve as substitute for the pressure ruby scale at high temperature, the breathing mode of bemsens (990 cm^?1) and the first order Raman mode of diamond (1333 cm^?1) have been studied as a function of pressure and temperature in the range of 0–15 GPa and 25–400°C. The diamond and bensene Raman frequency shifts are shoft to be of valuable use as a pressure scale at high temperature. A further advantage of bensene is to remain a suitable pressure transmitting medium up to 350°C and 15 GP.     

Calibration of the R ruby fluorescence lines in the pressure range [0-1 GPa] and the temperature range [250-300 K]

Abstract

The pressure range [&1 GPa] and the temperature range [250–300 K] are commonly used in many science fields like biology, agro-chemistry, pharmacology, or geology. In this paper, the calibration of the ruby R lines of fluorescence is performed in these pressure and temperature ranges, using the melting curve of pure water. The linear shifts of ruby peaks are equal to ?0.140cm^?1/K and ?0.768cm^?1/kbar with R₁, and to ?0.137cm^?1/K and ?0.779 cm^?1/kbar with R₂. The accuracy of pressure measurements can be as good as ± 10MPa if the temperature is known with ±0.5 K. Such a precision is achieved if: (1) the position of each peak is determined using an inversion method; (2) daily shifts of the spectrometer are corrected before each acquisition; (3) peak positions of each ruby are known at ambient pressure and temperature.     

Transformation of the magnetic structure of FeBO<Subscript>3</Subscript> under high pressures

The transformation of magnetic structure under hydrostatic and quasi-hydrostatic pressures up to 4 GPa was studied for iron borate FeBO₃ by the neutron diffraction method. Under quasi-hydrostatic conditions, the orientation of iron magnetic moments changes at pressures P≥1.4 GPa. Under hydrostatic conditions, no changes in the magnetic structure of iron borate were observed up to 2.1 GPa. This behavior is caused by the influence of the inhomogeneity (in magnitude and direction) of elastic stresses on the configuration of magnetic sublattices.     

Compression behavior of NiO in a diamond cell

Abstract

The compressibility of synthetic polycrystalline NiO was studied in a diamond anvil cell at room temperature utilizing two different X-ray sources. A standard film with a conventional X-ray source and the energy dispersive X-ray diffraction (EDXRD) method with synchrotron radiation were used for data acquisition. In the film method, the sample was compressed in a 4:1 methanol to ethanol solution up to 7 GPa with ruby fluorescence as a pressure calibrant. In the energy dispersive method, NiO powder was mixed with gold and compressed in two different conditions: gasketed and ungasketed up to 30 GPa. In the gasketed run, water was used as the pressure transmitting medium while gold was used as pressure calibrant in both runs.

Hydrostatic compression of NiO in both diffraction methods yields a bulk modulus (K _o) of 187 ± 7 GPa assuming K′ = 4. The compression of gasketed NiO of the synchrotron experiment, however, showed an obvious break at pressure exceeding 4 GPa due to the loss of hydrostaticity. NiO in a nonhydrostatic condition behaves with less compressibility than the hydrostatic results with a nominal K _o of 238 ± 10 GPa. The lower compressibility of NiO in synchrotron runs is attributed to the uniaxial loading effect which was more easily detected by the EDXRD geometry. The discrepancy in the bulk modulus can be attributed to the contrast in the shear strength between the sample and pressure medium and the Poisson effect of the sample under uniaxial loading.     

Pressure-induced dimerization of C60 fullerene

The dimerization of C₆₀ fullerene under conditions of quasi-hydrostatic compression at temperatures above 293 K is investigated by IR spectroscopy, Raman scattering (RS) spectroscopy, and x-ray diffraction. The measured dimer (C₆₀)₂ content in the products of the polymerization of fullerite as a function of the pressure, temperature, and treatment time shows that dimerization occurs even at room temperature in the entire pressure range above ∼1.0 GPa. However, at least at temperatures above 400 K dimerization does not result in the formation of a dimer phase as a stable modification of the system, since the dimer is an intermediate product of the transformation. It is shown that increasing the holding time at 423 K decreases the content of the dimer fraction in the samples and results in the formation of linear (at 1.5 GPa) and two-dimensional (at 6.0 GPa) polymers, which are structure-forming elements of the orthorhombic and rhombohedral polymerized phases. Pis'ma Zh. éksp. Teor. Fiz. 68, No. 12, 881–886 (25 December 1998)     

High-pressure effect on inverse spinel LiCuVO4:X-ray diffraction and Raman scattering

The effect of external quasi-hydrostatic pressure on the inverse spinel structure of LiCuVO 4 was studied in this paper. High-pressure synchrotron X-ray diffraction and Raman spectroscopy measurements were carried out at room temperature up to 35.7 and 40.3 GPa, respectively. At a pressure of about 20 GPa, both Raman spectra and X-ray diffraction results indicate that LiCuVO4 was transformed into a monoclinic phase, which remained stable up to at least 35.7 GPa. Upon release of pressure, the high-pressure phase returned to the initial phase. The pressure dependence of the volume of low pressure orthorhombic phase and high-pressure monoclinic phase were described by a second-order Birch-Murnaghan equation of state, which yielded bulk modulus values of B 0 = 197(5) and 232(8) GPa, respectively. The results support the empirical suggestion that the oxide spinels have similar bulk modulus around 200 GPa.     

High-pressure optical studies on R-line fluorescence lifetime in Al2O3:V2+

The effect of high hydrostatic pressure (up to 10.3?GPa) at room temperature on fluorescence lifetime τ for R line (²E→⁴A₂ transition) in ruby Al₂O₃:V²⁺ was studied. The performed studies show the linear increase of τ with increasing pressure. At 10.3?GPa, τ is about 1.36 times higher than at ambient pressure. The obtained trend was explained by a model which considered the effect of pressure on τ through an induced change of line position, inter-ionic distance, compressibility, and molecular polarizability. A good agreement between the calculated and experimental values for τ was obtained.     

Hysteresis of ruby fluorescent line by pressure and annealing effect

Abstract

Accuracy of hydrostatic pressure measurement in a diamond-anvil cell (DAC) depends on the reproducibility of ruby RI fluorescent measurement. The larger scatter in R, fluorescent wavelength shift than the reproducibility of spectroscopic measurement was observed among appropriately mirror-finished ruby plates before setting up in DAC. The characteristics of the scatter changed after loading DAC up to pressure over hydrostatic limit. They vanished by annealing the ruby plates. These phenomena are presumably due to the appearance and disappearance of the residual stress in the ruby crystal. Such hysteresis of ruby fluorescent wavelength shift by pressure and its annealing effect are discussed.     

钙钛矿（GaTiO3）高压相变及等温压缩

 高温高压条件下对钙钛矿（Perovstsite）多晶进行了研究，在金刚石压砧设备上压力条件最高达38 GPa，YAG莱塞加热温度近1 000 ℃以上，用红宝石荧光校压系统进行压力标定。实验结果表明静水压条件X射线就位测量，GaTiO₃(Ⅰ)由斜方晶系在10 GPa时直接向六方GaTiO₃(Ⅱ)结构相变，体积变化为1.6％；1 000 ℃加热及其非静水压条件下GaTiO₃(Ⅰ)由斜方晶系首先转变为四方晶系GaTiO₃(Ⅲ)转变压力为8.5 GPa，体积变化为0％，继续增加压力导15 GPa，GaTiO₃(Ⅲ)向GaTiO₃(Ⅱ')转化成六方晶系，体积变化亦为1.6％。三种高压相，在压力降到一个大气压时都会消失，所以是逆转化的非淬火相。等温压缩在标准静水压条件下进行，压力应小于10.4 GPa，K₀'=5.6时，K₀=(210±7)GPa，此数据是根据Birch-Murnaghan状态方程求得的体模量。     

传压介质对晶格振动和相变压力的影响——α-Bi2O3的高压拉曼光谱研究

 本文分别使用4∶1的甲醇-乙醇混合溶液和固态氩做传压介质测量α-Bi₂O₃的高压拉曼光谱。实验结果表明，传压介质对样品的谱线频移速率及相变压力有明显的影响。通过对拉曼光谱的分析认定，α-Bi₂O₃在高压下可能经历了一次结构相变，在准静水压和非静水压条件下的相变压力分别为23.1 GPa和20.4 GPa。     

Ruby under pressure

The ruby luminescence method is widely used for pressure measurement in the diamond anvil cell and other optically transparent pressure cells. With this application in mind, we briefly review the ground-state physical properties of corundum (α-Al₂O₃) with some emphasis on its behavior under high pressure, survey the effects of temperature and stress on the R-line luminescence of ruby (Cr-doped corundum), and address the recent efforts towards an improved calibration of the R-line shift under hydrostatic pressures beyond the 50 GPa mark.     

Diamond and cubic boron nitride under high pressure: Raman scattering,equation of state and high pressure scale

Abstract

The development of the diamond-anvil cell has stimulated Raman-scattering investigation of vibrational modes in covalent crystals. The linear pressure coefficient reported for diamond by Hanfland et at' (2.90 ± 0.05 cm-¹/GPa) agrees to within mutual experimental error with the result of Boppard et aL² (2.87±0.01 cm-¹/GPa). As to cubic boron nitride, the only work by Sanjurjo ef aL3 reports 3.45 ± 0.07 cm-¹/GPa for LO- and 3.39 ± 0.08 cm-¹/GPa for TO- modes. Since no compressibility data are availablel^1?3, the mode Griineisen parameter γ = ‐ δ In γ/δ is defined as y = K/Y·dv/aP and depends on the bulk modulus K and the calibration of the ruby scale. The above papers report y= 0.96 and y=0.95±O.O3fordiamondand γ_Lo=1.21,γTo=1.51 forBN.     

Metallization of Cu3N Semiconductor under High Pressure

Using the four-probe method, we investigate the electrical conductivity of Cu3N under high pressure with the diamond anvil cell. Cu3N is a semiconductor at ambient pressure showing a band gap about l eV. With the application of quasi-hydrostatic pressures, its resistance decreases dramatically over five orders of magnitude from ambient to 9 GPa. The compound became a metal at pressure about 5.5 GPa, which is in well agreement with the recent first principle calculation.     

On the high-pressure phase transition in

X-ray diffraction (XRD) experiments have been carried out on quartz-like GaPO₄ at high pressure and room temperature. A transition to a high pressure disordered crystalline form occurs at 13.5 GPa. Slight heating using a YAG infrared laser was applied at 17 GPa in order to crystallize the phase in its stability field. The structure of this phase is orthorhombic with space group Cmcm. The cell parameters at the pressure of transition are a =7.306?, b =5.887? and c =5.124?. Received: 7 October 1997 / Received in final form: 17 November 1997 / Accepted: 18 November 1997