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1.
A systematic investigation on the fluorescent spectra of SrB4O7:Sm2+ was performed in detail at high-temperature up to 623?K and/or high pressure up to 23.2?GPa with different pressure-transmitting media (PTMs), respectively. Combined with experiment data of previous research, the change of the 7D05F0 line (0–0 line) full width at half maximum (FWHM) of SrB4O7:Sm2+ under different pressure environments was specifically discussed. The results indicate that the FWHM of 0–0 line is sensitive to the non-hydrostatic pressure environment in 2-propanol, and methanol and ethanol mixture (ME) PTMs at ambient temperature. The first-order and the second-order derivation of the temperature dependence of 0–0 line FWHM at ambient pressure are 1.48(±0.21)?×?10?4?nm/K and 9.63(±0.63)?×?10?7?nm2/K2 below 623?K. The 0–0 line FWHM is also sensitive to the non-hydrostatic pressure environment in ME at high-temperature and high pressure simultaneous, the non-hydrostatic transition pressures are 9.6?GPa at 323?K, 11.0?GPa at 373?K, 14.4?GPa at 423?K, respectively. SrB4O7:Sm2+ is recommended as an optical sensor to reflect the change of pressure environment in liquid media at high-temperature and/or high pressure.  相似文献   

2.
The fluorescence lifetime for magnetic dipole 5D07F1 transition in yttrium aluminum garnet doped with Eu3+ (YAG:Eu3+) crystal was studied under the pressure of up to 10.4?GPa at room temperature. The fluorescence lifetime τ (5D07F1 transition) slowly decreased with pressure. The pressure effect on τ (5D07F1 transition) was explained with a model which considered pressure effect on line position: inter-ionic distance, ion volume, molecular volume, ion polarizability, molecular polarizability, sample refractive index, and surrounding hydrostatic medium refractive index. The fluorescence lifetime τ calculated by the presented model was in close correspondence with the experimental values.  相似文献   

3.
Abstract

The fluorescence spectra of Y2O3:Eu3+ nanoparticles have been measured under the pressure of up to 78 kbar at room temperature. In this pressure range, a red-shift of 0.02(1) nm/kbar?1 is noticed for the 0–2 line (5D07F2 transition). This shift is explained by the change of negative charge of the surrounding ligands. Compatibility between measured and calculated values for the 0–2 line position was obtained. The luminescence decay curves of the 5D07F2 transition were studied up to 78 kbar and were found to behave exponentially for all pressures studied. The fluorescence lifetime τ for the 0–2 line (5D07F2 transition) slowly decreased with pressure. The pressure effect on τ for the 0–2 line (5D07F2 transition) was explained by a model which considers the pressure effect on the line position, inter-ionic distance, ion volume and polarizability, molecular volume and polarizability, molecular refractive index and the refractive index medium n med of the surrounding hydrostatic medium. The fluorescence lifetime calculated by the present model is in close correspondence with the experimental values.  相似文献   

4.
This study considers the effects of hydrostatic pressure on the line position and fluorescence lifetime τ for 5D07F2 transitions in GdVO4: Eu3+ nanocrystals. The results indicate that the pressure induced the red shift toward longer wavelengths for all the considered lines with different rate. The fluorescence lifetime τ nonlinearly decreases with pressure in the considered pressure range. High pressure induced the fluorescence lifetime τ that can be explained with a simple theoretical model. The measured line position and τ are in a satisfactory agreement with the theoretical calculations.  相似文献   

5.
Photoluminescence spectra of Sm2+-doped BaBr2 have been measured under hydrostatic pressures up to 17 GPa at room temperature. In the low pressure range a red-shift of the broad 5d-4f transition of −145 cm−1/GPa is observed. From 5 to 8 GPa a phase mixture of the initial orthorhombic phase and the high-pressure monoclinic phase gives rise to two 5d-4f bands, which are strongly overlapping. Above 8 GPa the crystal is completely transformed to its high-pressure phase where two different Sm2+ sites exist, but only one broad 5d-4f transition is detected. It exhibits a red-shift of −36 cm−1/GPa. In addition, the line shifts of the 5D07FJ (J=0, 1, 2) transitions are investigated. Linear shifts of −19 cm−1/GPa for J=0, 2 and of −13 cm−1/GPa for J=1 are observed in the pressure range from 0 to 5 GPa.  相似文献   

6.
Abstract

Luminescence spectra from Eu3 + ion in B-type (monoclinic) 2O3 powder have been recorded at room temperature as a function of pressure using a diamond anvil cell. Changes in the spectral pattern of the Eu3 + ion emission at about 4 GPa indicated that a phase transition to the A-type (hexagonal) structure had taken place. Upon release of the applied pressure, the B-type structure was regained with hysteresis. The spectral shifts with pressure have been used to study the effect of pressure on the spin-orbit interaction of the 4f electrons in the Ed + ion. The relationship between the relative changes in the spin-orbit coupling constant, ζ4f, and the volume accompanying the phase transition is also discussed.  相似文献   

7.
The pressure shift of 7D 0?5F 0 fluorescence line of SrB 4O 7:Sm 2+ has been recalibrated at high temperature and high pressure, respectively. Combined with the high pressure and high-temperature experimental data given by previous study, a quantitative analysis of the temperature effect on pressure shift of the 7D 0?5F 0 fluorescence line has been performed. The results show that there is an overall negligible coupling effect of temperature and pressure on the wavelength shift of the 7D 0?5F 0 fluorescence line below 770 K and 35 GPa. But above 770 K, the temperature effect on pressure shift could not be ignored at least in a relatively high pressure range. A proposed calibration relation is recommended to predict more accurate pressures in high pressure and high-temperature experiments with SrB 4O 7:Sm 2+ as the pressure scale.  相似文献   

8.
The behavior of Ca2AlFeO5 brownmillerite was studied by in situ synchrotron X-ray diffraction and Raman spectroscopy at 300?K with pressures up to 26.5 and 32.1 GPa, respectively. A reversible structural phase transition was observed. The P–V data were fitted by a third-order Birch–Murnaghan equation of state, and the isothermal bulk modulus was obtained as K0?=?181.9(76) GPa with K0?=?4.4(17). If K0′ was fixed to 4, K0 was obtained as 183.8(20) GPa. Ca2AlFeO5 brownmillerite shows an axial elastic anisotropy since the b-axis is more compressible than a- and c-axis. Combined with previous results, the isothermal bulk modulus and axial compressibility of Ca2AlFeO5 brownmillerite increase with more Al incorporated in the structure. The Raman spectra of Ca2AlFeO5 brownmillerite were analyzed and the pressure coefficients vary from 2.23 to 4.90?cm?1/GPa. The isothermal mode Grüneisen parameters range from 0.83 to 1.77 and the thermal Grüneisen parameter is determined as 1.08(11).  相似文献   

9.
ABSTRACT

In this paper, synthesis of titanium silicon carbide (Ti3SiC2) under high pressure and high-temperature condition has been investigated by using the reactant systems Ti/Si/C, Ti/SiC/TiC, Ti/SiC/C and Ti/TiC/Si. Results reveal that Ti/TiC/Si is unsuited to the synthesis of Ti3SiC2 under a high pressure of 2.0?GPa, while an elemental mixture of Ti/Si/C is applicable. By the addition of Al, Ti3SiC2 with 95.8?wt% purity was obtained from elemental mixture with a large excess of silicon. The optimum experimental parameters were determined as Ti/Si/Al/C having the molar ratio of 3:1.5:0.5:1.9, holding at 2.0?GPa and 1300?°C for 60?min.  相似文献   

10.
ABSTRACT

The compressibility and effect of pressure on the vibrations of merrillite, Ca9NaMg(PO4)7, were studied by using diamond anvil cell at room temperature combined with in-situ synchrotron X-ray diffraction and Raman spectroscopy up to about 18 and 15?GPa, respectively. The pressure-volume data was fitted by a third-order Birch–Murnaghan equation of state to determine the isothermal bulk modulus as K0 ?=?87.2(32) GPa with pressure derivative K0?=?3.2(4). If K0′?=?4, the isothermal bulk modulus was obtained as 81.6(10) GPa. The axial compressibility was estimated and an axial elastic anisotropy exists since a-axis is less compressible than the c-axis. The Raman frequencies of all observed modes for merrillite continuously increase with pressure, and the pressure dependences of stretching modes (v 3 and v 1) are larger than those of the bending modes (v 4 and v 2) and external modes. The isothermal mode Grüneisen parameters and intrinsic anharmonicity of merrillite were also calculated.  相似文献   

11.
The structural, elastic, and electronic properties of SrZrN2 under pressure up to 100?GPa have been carried out with first-principles calculations based on density functional theory. The calculated lattice parameters at 0?GPa and 0?K by using the GGA-PW91-ultrasoft method are in good agreement with the available experimental data and other previous theoretical calculations. The pressure dependence of the elastic constants and the elastic-dependent properties of SrZrN2, such as bulk modulus B, shear modulus G, Young's modulus E, Debye temperature Θ, shear and longitudinal wave velocity VS and VL, are also successfully obtained. It is found that all elastic constants increase monotonically with pressure. When the pressure increases up to 140?GPa, the obtained elastic constants do not satisfy the mechanical stability criteria and a phase transition might has occurred. Moreover, the anisotropy of the directional-dependent Young's modulus and the linear compressibility under different pressures are analysed for the first time. Finally, the pressure dependence of the total and partial densities of states and the bonding property of SrZrN2 are also investigated.  相似文献   

12.
The post-corundum phase transition has been investigated in Ti2O3 on the basis of synchrotron X-ray diffraction in a diamond anvil cell and transmission electron microscopy. The new polymorph of Ti2O3 was found at about 19 GPa and 1850 K, and this phase was stable even at about 40 GPa. A new polymorph of Ti2O3 can be indexed on a Pnma orthorhombic cell, and the unit-cell parameters are a=7.6965 (19) Å, b=2.8009 (9) Å, c=7.9300 (23) Å, V=170.95 (15) Å3 at 19 GPa, and a=7.8240 (2) Å, b=2.8502 (1) Å, c=8.1209 (3) Å, V=181.10 (1) Å3 at ambient conditions. The Birch–Murnaghan equation of state yields K 0=206 (3) GPa and K0=4 (fixed) for corundum phase, and K 0=296 (4) GPa and K0=4 (fixed) for the post-corundum phase. The molar volume decreases by 12% across the phase transition at around 20 GPa. The structural identification was carried out on a recovered sample by the Rietveld method, and a new polymorph of Ti2O3 can be identified as Th2S3-type rather than U2S3-type structure. The transition from corundum-type to Th2S3-type structure accompanies the drastic change of the form of polyhedron: from TiO6 octahedron in the corundum-type to TiO7 polyhedron in the Th2S3-type structures.  相似文献   

13.
张倩  巫翔  秦善 《中国物理 B》2011,20(6):66101-066101
In situ high-pressure experiments of Co2P are carried out by means of angle dispersive X-ray diffraction with diamond anvil cell technique. No phase transition is observed in the present pressure range up to 15 GPa at room temperature, even at high temperature and 15 GPa. Results of compression for Co2P are well presented by the second-order Birch-Murnaghan equation of state with V0 = 130.99(2)3 (1=0.1 nm) and K0 = 160(3) GPa. Axial compressibilities are described by compressional modulus of the axis: Ka = 123(2) GPa, Kb = 167(8) GPa and Kc = 220(7) GPa. Theoretical calculations further support the experimental results and indicate that C23-type Co2P is stable at high pressure compared with the C22-type phase.  相似文献   

14.
ABSTRACT

We present a theoretical study of the ground electronic state potential of the Ca+Ar2 complex and of its photoabsorption spectra, simulated at temperatures ranging between 20 and 220?K. These calculations exploit a Monte-Carlo (MC) method, based on a one-electron pseudo-potential approach. A pairwise additive potential fitted to coupled cluster ab initio points, is used to model the Ca+Ar2 complex. Our study shows that the most stable form of Ca+Ar2 is a bent C2v structure, whereas the linear isomer is located at around 90?±?10?cm?1 above in energy. The analysis of the photoabsorption spectra establishes that a structural transition from bent Ca+Ar2 to linear ArCa+Ar occurs at T~100?K. Trends in binding energies of both isomers, bond lengths and bond angles are also discussed. Molecular orbital overlaps provide an explanation for the order of stability between the bent and linear structures.  相似文献   

15.
Abstract

In the present investigation the excitation and fluorescence spectra and lifetimes of Mn2+ ions in calcium chloride, for various manganese concentrations and sample temperatures have been studied for the first time. The fluorescence spectrum consists of an asymmetric broad band, which upon lowering the sample temperature, shifts its maximum from 580 nm at 300 K to 596 nm at 11 K. This luminescence band was associated with the 4Tlg(4G)→6Alg(6S) spin-forbidden transition in the manganese ions occupying Ca-sites in the lattice of CaCl2. The excitation spectrum of the Mn2+ fluorescence revealed the features of manganese ions in octahedral coordination and consisted of nine excitation peaks which were associated with Mn2+-crystal-field-sensitive transitions. A crystal field analysis of the wavelength positions of these transitions by means of the model developed by Curie et al. allowed us to determine the magnitude of the cubic field splitting 10Dq, the reduced Racah parameter B', the Koide-Pryce covalency parameter ε and the spin transfer coefficients f [sgrave] and f σ. From the measurement of the temperature dependence of the Mn2+ fluorescence lifetime, we have also obtained information about the different mechanisms which are involved in the relaxation of excited Mn2+ ions in this host crystal in the temperature range (11–300 K).  相似文献   

16.
Abstract

A phase transition from Ca(OH)2 I (portlandite) to Ca(OH)2 II at high pressure and temperature has been confirmed, using in situ x-ray diffraction in a multianvil high pressure device (DIA). The structure was determined at 9.5 GPa and room temperature from data collected after heating the sample at 300°C at 7.2 GPa in a diamond anvil cell. Both the Le Bail fit and preliminary Rietveld refinement suggest that the new phase, which reverts to Ca(OH), I during pressure release, has a structure related to that of baddeleyite (ZrO1); it is monoclinic (P21/c) with a= 4.887(2), b= 5.834(2), c = 5.587(2), β = 99.74(2)°. The coordination number of Ca increases from six to seven (5 + 2) across the transition. At 500°C, the phase boundary is bracketed at 5.7 ± 0.4 GPa by reversal experiments performed in the DIA.  相似文献   

17.
The spin Hamiltonian parameters (SHPs) and the local structures for impurity W5+ in the Zn3(PO4)2ZnO nanopowders doped with WO3 under different concentrations are theoretically investigated using the perturbation calculations of these parameters. The exponential functions of the related quantities (cubic field parameter Dq, covalency factor N, relative tetragonal compression ratio τ and core polarisation constant κ) of concentration x with totally four adjustable coefficients a, b, c and d are adopted to fit the concentration dependences of the experimental d-d transition bands and SHPs. The impurity W5+ centres demonstrate moderate tetragonal compression ratios τ (~3.1%) due to the Jahn–Teller effect. With the increase of WO3 concentration, Dq and N show moderately decreasing rules, while τ and κ exhibit slightly and moderately increasing tendencies with x, respectively. The mechanisms of the above concentration dependences of these quantities are analysed from the modifications of the local crystal-field strength and electron cloud density around the impurity W5+ with the variation of x. Present theoretical studies would be useful to the exploration of the structural properties and optical applications for WO3 doped Zn3(PO4)2ZnO nanopowders.  相似文献   

18.
19.
Using a high-resolution Fourier transform spectrum recorded at SOLEIL for a rather large value of the (pressure?×?path length) product a new investigation of the very weak 2ν 1 absorption band of nitrogen dioxide, located at 2627.377?cm?1 was performed, together with an extension up to higher N and Ka values of a previous investigation of the strong ν 1?+?ν 3 band [J.-Y. Mandin, V. Dana, A. Perrin, J.-M. Flaud, C. Camy-Peyret, L. Régalia and A. Barbe, J. Mol. Spectrosc. 181, 379 (1997)]. The 2ν 1 lines proved to be perturbed by local vibration–rotation resonances which couple the (2,0,0) energy levels with those of the (1,2,0) and (1,0,1) states. Also the (1,0,1) energy levels are also coupled by a C-type Coriolis resonance with those of the (1,2,0) and (2,0,0) energy levels. The final energy levels calculation involves six interacting states of NO2, {(2,0,0), (1,2,0), (1,0,1), (0,0,2), (0,4,0), (0,0,2)}. An estimation of line intensities parameters was performed for the very weak 2ν 1 band. Finally a list of line parameters (positions, intensities and shapes) for the 2ν 1, ν 1?+?2ν 2 and ν 1?+?ν 3 bands of NO2, was generated and is now included in the GEISA database (https://geisa.aeris-data.fr/).  相似文献   

20.
Infrared absorption and Raman study ofβ-Ni(OH)2 has been carried out up to 25 GPa and 33 GPa, respectively. The frequency ofA 2u internal antisymmetric stretching O-H mode decreases linearly with pressure at a rate of −0.7 cm1/GPa. The FWHM of this mode increases continuously with pressure and reaches a value of ∼ 120 cm−1 around 25 GPa. There was no discernible change observed in the frequency and width of the symmetric stretchingA 1g O-H Raman mode up to 33 GPa. The constancy of the Raman mode is taken as a signature of the repulsion produced by H-H contacts in this material under pressure. Lack of any discontinuity in these modes suggests that there is no phase transition in this material in the measured pressure range.  相似文献   

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