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1.
Abstract

The onset critical temperature T co, of CaLaBaCu3O7, is measured as a function of pressure by means of a cryogenic diamond anvil cell. We find ?T co/?p = 0.14 ± 0.02K/GPa. The pressure dependence of the upper critical field B c2 as a function of pressure is determined for T/Tc , = 0.96. From this we found the corresponding volume dependence of the number of charge carriers to be much smaller than the value derived from Hall effect measurements in YBa2Cu3O7.

Les dérivées par rapport à la pression de la température critique supérieure Tco , (avec ?T co,??p = 0.14 ± 0.02K/GPa) et du champs critique B c2 à T/Tc , = 0.96 ont été déterminé á l'aide d'une presse à diamants. Pour le composé CaLaBaCu3O7, la variation de la densité de charges en fonction du volume est beaucoup plus faible que celle détermiée par effet Hall dans YBa2Cu3O7.  相似文献   

2.
黄晓丽  李芳菲  黄艳萍  吴刚  李鑫  周强  刘冰冰  崔田 《中国物理 B》2016,25(3):37401-037401
The high-pressure behavior of solid hydrogen has been investigated by in situ Raman spectroscopy upon compression to 300 GPa at ambient temperature. The hydrogen vibron frequency begins to decrease after it initially increases with pressure up to 38 GPa. This softening behavior suggests the weakening of the intramolecular bond and the increased intermolecular interactions. Above 237 GPa, the vibron frequency softens very rapidly with pressure at a much higher rate than that of phase III, corresponding to transformation from phase III into phase IV. The phase transition sequence has been confirmed from phase I to phase III and then to phase IV at 208 and 237 GPa, respectively. Previous theoretical calculations lead to the proposal of an energetically favorable monoclinic C2/c structure for phase III and orthorhombic Pbcn structure for phase IV. Up to 304 GPa, solid hydrogen is not yet an alkali metal since the sample is still transparent.  相似文献   

3.
Abstract

Copper oxide has been studied at high pressure up to 50 GPa. A monoclinic structure was compatible with the measurements at all pressures, and no phase change was observed. A bulk modulus, B0, = 98 GPa, and its pressure derivative B′0 = 5.6 was obtained.  相似文献   

4.
Abstract

By means of a four-point resistivity method the critical temperature (Tc) of the tetragonal high temperature super-conductor CaLaBaCu3Ox was studied for pressures up to 9 GPa. The pressure dependence of Tc is small and negative, dTc/dp = - 0.77 K/GPa, and agrees with the general trend observed in previous data.  相似文献   

5.
PbTe has been investigated using synchrotron X-ray diffraction (XRD) in a diamond anvil cell under quasi-hydrostatic pressures up to 50 GPa. Upon compression to 6.6 GPa, the initial NaCl phase transforms to an intermediate phase, which is confirmed to be an orthorhombic structure with a space group Pnma. At 18.4 GPa, the intermediate Pnma phase undergoes a phase transition to the CsCl structure. The systemic analysis of the crystal structures between the NaCl and intermediate phases indicates that the structure of the Pnma phase could be derived from the distortion of the NaCl structure. The bulk modulus of the CsCl phase is B0=52(2) GPa with V0=60.8(4) Å3 and B0=4.0 (fixed), slightly larger than the NaCl phase (B0=44(1) GPa) and the intermediate phase (B0=49(3) GPa).  相似文献   

6.
Abstract

Neptunium and plutonium monosulfides were studied under high pressure up to ~60 GPa using a diamond anvil cell in an energy dispersive X-ray diffraction facility. The compounds, of cubic rock salt structure type at ambient pressure, do not show any crystallographic phase transition in the domain of investigation. From the pressure-volume relationship, we determined bulk moduli of 92 and 120 GPa with pressure derivatives of 4.6 and 4.1 for NpS and PUS respectively.  相似文献   

7.
The structural transformation of cesium lead iodine (CsPbI3) has been investigated in diamond anvil cells up to ~15 GPa at room temperature by employing synchrotron radiation X-ray diffraction and Raman spectroscopy. One reversible transformation from orthorhombic (Pnma) to monoclinic (P21/m) phase has been observed at 3.9 GPa. Isothermal pressure–volume relationship of orthorhombic CsPbI3 is well fitted by the third-order Birch–Murnaghan equation of state with K0 = 14(3) GPa, K′0 = 6(2) and V0 = 891(7) Å3. The ultralow value of bulk modulus K0 demonstrates the high compressible nature of CsPbI3, similar to those of organic–inorganic metal halide perovskites. The present results provide essential information on the intrinsic properties and stability of CsPbI3, which may be applied in photovoltaic devices.  相似文献   

8.
The effect of pressure on the Raman modes in TeO2 (paratellurite) has been investigated to 30GPa, using the diamond cell and argon as pressure medium. The pressure dependence of the Raman modes indicates four pressure-induced phase transitions near 1 GPa, 4.5 GPa, 11 GPa and 22 GPa. Of these the first is the well studied second-order transition fromD 4 4 symmetry toD 2 4 symmetry, driven by a soft acoustic shear mode instability. The remarkable similarity in the Raman spectra of phases I to IV suggest that only subtle changes in the structure are involved in these phase transitions. The totally different Raman spectral features of phase V indicate major structural changes at the 22GPa transition. It is suggested that this high pressure-phase is similar to PbCl2-type, from high pressure crystal chemical considerations. The need for a high pressure X-ray diffraction study on TeO2 is emphasized, to unravel the structure of the various high pressure phases in the system.  相似文献   

9.
 运用金刚石对顶砧(Diamond Anvil Cell,DAC)技术,以液氩作为传压介质,在最高压力为67 GPa的压力范围内对NiO进行了原位的同步辐射X射线衍射研究。在整个实验过程中,并未发现第一类结构相变,也没有发现T.Sasaki等预测的在60 GPa左右轴比c/a随压力的变化率而突然增大的现象,且此压力范围内NiO的结构畸变程度随压力的变化趋势相比以前的研究结果要平缓一些。用三阶的Brich-Murnaghan方程对实验数据进行拟合,得到的体弹模量及其对压力的一阶导数分别为B0=195(4) GPa和B0′=5.3(2)。  相似文献   

10.
The present paper reports the results of in situ Raman studies carried out on nano-crystalline CeO2 up to a pressure of 35 GPa at room temperature. The material was characterized at ambient conditions using X-ray diffraction and Raman spectroscopy and was found to have a cubic structure. We observed the Raman peak at ambient at 465 cm?1, which is characteristic of the cubic structure of the material. The sample was pressurized using a diamond anvil cell using ruby fluorescence as the pressure monitor, and the phase evolution was tracked by Raman spectroscopy. With an increase in the applied pressure, the cubic band was seen to steadily shift to higher wavenumbers. However, we observed the appearance of a number of new peaks around a pressure of about 34.7 GPa. CeO2 was found to undergo a phase transition to an orthorhombic α -PbCl2-type structure at this pressure. With the release of the applied pressure, the observed peaks steadily shift to lower wavenumbers. On decompression, the high pressure phase existed down to a total release of pressure.  相似文献   

11.
12.
Abstract

Ni-H and Re-H binary systems have been studied at room temperature by X-ray diffraction in a diamond-anvil cell. The formation of the hydrides NiH and ReHo.4 with no change in the types of the host metal lattices was observed through the expansion of the host lattices. No structure changes were observed in the metal sub-lattice of either hydride under increasing pressure and the equations of state have been obtained to 123GPa. The difference in the partial hydrogen volume as a function of pressure between the Ni-H and Re-H systems can be understood with reference to the behaviour of conduction electrons. The pressure dependence of the partial hydrogen volume in these hydrides supports the hypothesis of the apparent common-volume behaviour of hydrogen in a metallic environment.  相似文献   

13.
14.
Abstract

The melting curve of NaCl0.5Br0.5 has been measured under pressure up to 4.5 GPa. The melting temperatures of Ag and NaCl have been used to determine the pressure in the sample at its melting temperature.  相似文献   

15.
Abstract

The high-pressure crystal structures of Th3P4 and U3X4, where X = P, As and Sb, have been studied by means of synchrotron x-ray diffraction in the pressure range up to 50 GPa. The cubic phase of these compounds is retained in the whole pressure range. The bulk modulus B0 and its pressure derivative B0’ have been determined for each compound. A log-log plot of B0 versus unit-cell volume gives a straight line for the uranium pnictides, with a slope about -5/3.  相似文献   

16.
A kinetic study of phase transformation of n-octane has been performed using a hydrothermal diamond anvil cell. The results show that pressure has a negative effect on the solid–liquid reaction rate. The increase of pressure can accelerate the liquid–solid transformation rate. Upon the liquid–solid transformation, the light transmittance showed a decreased trend with time in the early stage, which was caused by the formation of a large quantity of crystal nuclei. In the later stage, the light transmittance almost remained the same, thus indicating a growth stage of crystal nuclei. The activation volume yields a value of 2.16×10?5 and –1.35×10?5 m3/mol for the solid–liquid and liquid–solid transformations. Based on the obtained activation energy, the solid–liquid transformation is dominated by the interfacial reaction and diffusion, and the liquid–solid transformation is controlled by diffusion. This technique is an effective and powerful tool for the transformation kinetics study of n-octane.  相似文献   

17.
ABSTRACT

Nano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25?GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ~1700°C at 15?GPa to ~1900°C at 25?GPa. The NPD having grain sizes less than ~50?nm was synthesized at temperatures below ~2000°C at 15?GPa and ~2300°C at 25?GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10?nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions.  相似文献   

18.
Abstract

The high-pressure crystal structures of the compounds UX, where X = N, P, As and Sb, have been studied using X-ray diffraction in the pressure range up to about 60 GPa Rhornbohedral distortions are observed for UN and Up above 29 GPa and lO GPa, respectively. In Up a further transformation to an orthorhombic phase occurs at 28 GPa. UAs and USb transform to the CsCl structure at 20 GPa and 9 GPa, respectively. The latter transformations show a considerable hysteresis when the pressure is released. The scaling behaviour of the bulk modulus has been studied. It is confirmed that a log-log plot of bulk modulus versus specific volume for the cubic phases gives a straight line with a slope near ? 5/3.  相似文献   

19.
Results of X-ray powder diffraction measurements up to 35 GPa carried out on GaCMn3 are presented. GaCMn3 does not undergo any structural transition in this pressure region. However, the pressure–volume data can be fitted to two straight line segments in the pressure regions; one from 0 to 5 GPa and another from 5 to 30 GPa respectively.  相似文献   

20.
In situ X-ray diffraction measurements on germanium were conducted in the pressure range of 5-11 GPa and temperatures up to 950 K. Using our data a better defined P-T diagram for germanium is presented. The coordinates of the triple point between GeI-GeII-GeL have been determined to a better degree of precision. The onsets of the GeI-GeII transition were found both under hydrostatic and non-hydrostatic conditions. Anisotropy of thermal expansion coefficient for the GeII is characterized from the c/a ratios in the temperature interval 473-823 K. Phases GeIII and GeIV are shown to be metastable forms of germanium.  相似文献   

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