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X-ray diffraction study of Sb has been made under the pressure of up to 43 GPa. A new phase transition from the Sb(III) into a b.c.c. phase occurs at about 28 GPa. The b.c.c. phase is found to be stable for the wide range of pressure from 28 GPa to at least 43 GPa. 相似文献
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Electron Transport Property of CdTe under High Pressure and Moderate Temperature by In-Situ Resistivity Measurement in Diamond Anvil Cell
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In situ resistivity measurement has been performed to investigate the electron transport property of powered CdTe under high pressure and moderate temperature in a designed diamond anvil cell. Several abnormal resistivity changes can be found at room temperature when the pressure increases from ambient to 33 GPa. The abnormal resistivity changes at about 3.8 GPa and 10 GPa are caused by the structural phase transitions to the rock-salt phase and to the Cmcm phase, respectively. The other abnormal resistivity changes at about 6.5 GPa, 15.5 GPa, 22.2 GPa and about 30 GPa never observed before are due to the electronic phase transitions of CdTe. The origin of the abnormal change occurred at about 6.5 GPa is discussed. The temperature dependence of the resistivity of CdTe shows its semiconducting behaviour at least before 11.3 GPa. 相似文献
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金红石高温高压相变的Raman光谱特征 总被引:3,自引:2,他引:1
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。 相似文献
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Ming Li Wuming YangLixin Li Huixin WangShaowei Liang Chunxiao Gao 《Physica B: Condensed Matter》2011,406(1):59-62
High pressure behavior of CaB6 with cubic crystal structure is investigated by means of energy dispersive X-ray diffraction and by employing in situ resistance measurement in a diamond anvil cell. Two newcome high pressure phase transitions are found with pressure ranging from ambient to 26 GPa. The first one at 12 GPa is a structural phase transition from CsCl-type structure to orthogonal structure, which is reflected by both the X-ray diffraction and the resistance variation. The other one at 3.7 GPa is suggested to be an electronic transition, which is observed only in resistance measurement. The diffraction pattern recovered while the pressure is released to 0 GPa with a pressure hysteresis over 11 GPa, which implies the reversibility of the two phase transitions. Bulk moduli of the cubic and orthogonal phases are estimated by fitting the data to a Brich-Murnaghan equation of state equal to 169.9 and 48.2 GPa, respectively. 相似文献
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动载下剪应力对相变起始压力有无影响,长期以来一直是一个未解决的问题。Duvall和Graham建议用硫化镉(CdS)晶体来作为判断材料。本文采用前后压电石英传感器方法系统地研究了高速平面撞击下的c轴CdS单晶试样中剪应力对相变起始压力的影响。实验测得其轴向相变起始应力为σT=(3.25±0.1) GPa,对应的平均压力pT=(2.29±0.07) GPa,与静高压值2.3 GPa相比在实验误差范围内很吻合,这时相应的剪应力τT=0.72 GPa,高达平均压力的31.5%。这一结果表明,相变机制可以假定为仅与临界平均应力或临界热力学状态有关,剪应力对相变起始压力的影响可以忽略。 相似文献
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Structural behaviour of cyclo-octane under high pressure is studied by using a synchrotron x-ray source in a diamond anvil cell (DAC) up to 40.2 GPa at room temperature. The cyclo-octane firstly solidifies to the triclinic phase at 0.87 GPa. With the increasing pressure, the phase of cyclo-octane changes to the tetragonal phase at about 6.0 GPa and then transforms to amorphous phase above 18.2 GPa, which is kept till to 40.2 GPa. All the phase transitions of cyclo-octane are irreversible. 相似文献
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A high-pressure Raman study was carried out on NaAlH4 up to 17 GPa using the diamond anvil cell method. In the pressure region 2–5 GPa, several of the original modes split. Although this might be a sign of some structural change, the spectral changes do not allow us to claim the existence of a clear phase transition in this pressure range. The spectra revert to their ambient pressure forms on decreasing pressure below<3.0–1.4 GPa. A phase transition to β-NaAlH4 was found at 14–16 GPa. This phase transition is also reversible with an unusually strong hysteresis: the β-NaAlH4 can be followed upon decompression down to 3.9 GPa. Analysis of Raman data shows that this phase transition is compatible with a theoretical prediction of a strong volume collapse. 相似文献
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系统地研究了在0~3 MPa氧压下T1系超导材料的制备过程及其超导性质。结果表明:0.25~0.90 MPa氧压下所制备的样品为纯2223相,Tc0最高可达125.3 K;1.45~3.00 MPa氧压下样品为纯2212相,Tc0在95~100 K之间;0.90~1.45 MPa氧压下样品为2223及2212两相共存。对两种单相样品的高压研究结果表明,2223相样品比2212相样品有着较强的压力效应,在0~0.52 GPa压力下分别为4.0 K/GPa及2.0 K/GPa。 相似文献
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Electrical properties of stoichiometric iron sulfide (FeS) are investigated under high pressure with a designed diamond anvil cell. The process of phase transition is reflected by changing the electrical conductivity under high pressure, and the conductivity of FeS with the NiAs structure is found to be much smaller than other phases. Two new phase transitions without structural change are observed at 34.7 GPa and 61.3 GPa. The temperature dependence of the conductivity is found to be similar to that of a semiconductor when the pressure is higher than 35 GPa 相似文献
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利用在金刚石压砧上集成的微电路,原位测量了CdSe多晶粉末在温度为300~450 K、压力达到23 GPa时电阻率随温度和压力的变化关系。实验结果表明:在加压过程中,电阻率在2.6 GPa压力时出现的异常改变,对应着CdSe从纤锌矿向岩盐矿结构的转变,而在6.0、9.8、17.0 GPa等压力处出现的电阻率异常,则是由CdSe中的电子结构的变化所引起的;在卸压过程中,只在约14.0和3.0 GPa压力下观察到了两个电阻率异常点。通过对电阻率随压力变化曲线的模拟,得出了CdSe高压相的带隙随压力的变化关系,据此预测CdSe金属化的压力应在70~100 GPa之间。变温实验结果表明,在实验的温度和压力范围内,CdSe的电阻率均随温度的增加而升高。 相似文献
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以Ar作压力介质,在0~23 GPa压力范围内,利用金刚石压腔装置(DAC)和激光加温技术,采用显微拉曼光谱进行原位测试,对处于准静水压力条件下的斜锆石开展高温高压相变研究。研究结果表明:室温下斜锆石ZrO2于3.4 GPa时开始发生相变,到10.4 GPa时其明显转变成一个空间群为Pbca的斜方相。此新相随着压力升高,直到15.3 GPa,仍稳定存在。通过研究,首次获得了Pbca相的拉曼谱图。随后在15.3 GPa压力下进行了激光加温后淬火,结果发现,加热前的Pbca相又转变成了空间群为Pnam的PbCl2结构类型的高压相,该相直到实验最高压力23 GPa仍稳定存在。 相似文献
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Abstract Plutonium monoselenide was studied under high pressure up to 47 GPa, at room temperature, using a diamond anvil cell in an energy dispersive X-ray diffraction facility. At ambient pressure, PuSe has the NaC1-type (B1) structure. The compound has been found to undergo a second-order crystallographic phase transition at around 20 GPa. This phase can be described as a distorted B1 structure, with a rhombohedral symmetry. PuSe transforms to a new phase at around 35 GPa, which can be indexed in the cubic CsCl-type (B2). The volume collapse at this phase transition is 11%. When releasing pressure, we observed a strong hysteresis to the inverse transformation down to 5 GPa. From the pressure-volume relationship, the bulk modulus has been determined to B 0 = 98 GPa and its pressure derivative as B 0 = 2.6. These results are compared to those obtained with other actinide monmictides and monochalcogenides. 相似文献
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使用Bundy和Dunn发展起来的带有烧结金刚石砧的Drickamer型高压装置,用固定点测压法标定实验压力,在室温及0~43 GPa的压力范围内测量了稀土金属中Pr、Nd、Sm、Gd、Tb、Dy、Ho、Tm、Lu和Yb的电阻随压力的变化。在各稀土元素的电阻随压力变化的曲线上,观测到了若干“凸起”和斜率突变点,根据Jayaraman提出的三价稀土在压力作用下的相变顺序,得到了这些突(凸)变点分别对应着hcp→Sm-type→dhcp→fcc相变顺序中的某一类型的相变压力。此外还观测到了Pr、Gd、Tb的fcc相随着压力再增高而发生的相变,根据已报导的关于Pr的工作,推测Gd和Tb的这一相变应为fcc→dfcc相变,它们分别发生在22.0和24.5 GPa。在本工作所得结果基础上对Johansson的三价稀土总相图进行了修正。 相似文献
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Pressure-induced phase transition of anatase titanium dioxide was investigated by Raman, absorption spectroscopy and X-ray diffraction. The change in Raman and absorption spectra with pressure revealed that the transition from anatase to high pressure phase with f -PbO 2 structure (TiO 2 -II) occurred in the pressure range of 4.0-4.6 GPa for a single crystal. The X-ray powder diffraction patterns indicate the presence of superstructural lattice of anatase at pressures more than 3 GPa. The superstructure of anatase disappears on the release of the pressure. A sluggish transition to the high pressure phase is also observed. The anatase coexists with the high pressure phase at 5.2 GPa. The difference in the results between optical spectroscopy (single crystal) and X-ray diffraction (powder) will be due to crystalinity of the sample. 相似文献
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以化学水解法合成的β-FeOOH纳米微粉(平均粒径在12 nm左右)为原料,分别在0.0~4.5 GPa和200~350 ℃的压力和温度范围进行冷压和热压处理。实验结果表明,冷压对β-FeOOH纳米固体的结构没有明显影响,但却使它的热致相变(从β-FeOOH相到α-Fe2O3相)温度从常压下的203.8 ℃提高到4.5 GPa压力下的274 ℃,接近常规体相材料的相变温度。而在一定的热压条件处理下,首次发现了从β-FeOOH相到α-FeOOH相的结构转变,并在4.5 GPa、200 ℃的热压条件下得到了转变过程中的一个新的亚稳相。从压力和温度对纳米微粒的作用角度,对上述实验结果进行了讨论。 相似文献
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Haibo Xiao Ruilong Wang Linfang Xu Fujun Yang Changping Yang 《Physics letters. A》2018,382(4):224-230
First-principles calculations are performed to investigate pressure effects on structure, magnetism, martensitic phase transition and Curie temperatures of Mn2PtGa Heusler alloy in framework of the density functional theory. It is shown that Mn2PtGa prefer to crystallize in the inverse Heusler type structure. Besides, we predict an extraordinary occurrence of pressure induced metallic ferrimagnetism to half-metallic ferromagnetism transition in cubic phase of Mn2PtGa alloy under hydrostatic pressure up to 43 GPa and the half-metallic ferromagnetism is found to be robust even the lattice further compression to 90 GPa. However, with the pressure up to 100 GPa, the spin-down gap starts to close and the half metallicity begin to disappear, while with the pressure increasing from 100 GPa to 300 GPa, the alloy returns to metallic characteristic. In addition, the energy difference between the austenitic and martensitic phases is found to increase with increasing pressure followed by a decrease when pressure reaches to 43 GPa, which implies a variation trend of martensitic phase transition temperature. Furthermore, Curie temperatures in both austenitic and martensitic phases are estimated under pressure by using the standard mean-field approximation which agrees well with the theoretical results in literature. The robustness of the half metallicity, magnetic transition and the high Curie temperature under pressure make Mn2PtGa alloy a promising candidate for applications in spintronic devices. 相似文献