Infrared Spectra of Morfolonium (mpH)2Mo2Cl6(H20)2(I),(mpH)2Mo2ClxBr6-x(H2O)2(II)/ (mpH)2Mo2Br6(H2O)2(III) and the Pyridinium (PyH)2Mo2I6(H2O)2(IV)Hexahalo-di(aquo): dimolybdate(II) Complexes,Containing Quadruple Metal-Metal Bounds

Abstract

The electronic (800–400 nm), infrared (4000–200,400–20 cm^?1), ordinary Raman (400–200 cm^?1) spectra of morpholinium and the pyridium hexahalo-di(aquo) dimolybdate(II) complexes, containing quadruple metal-metal bonds were investigated. The electronic spectra of the solid compounds at various temperatures (25,100 and 300K) demonstrate intense and structured bands in the visible region (510–582 nm) attributed to the expected δ→δ? transitions.

From the infrared and Raman spectra, the skeletal stretching modes in these complexes have been localized, and the charectenstic bands of these ions were observed in the expected regions.

Finally, the ionic interections were relatively weak, but the existance of phenomena was perceptible and the result was obtained in agreement with X-ray data.     

Pressure Induced Phase Transition in Solid Oxygen at 1.8 K

Pressure dependence of Raman scattering in solid oxygen was studied at 1.8 K. When the f phase is compressed, two libron peaks that, increasing pressure, merge smoothly with those of the l phase at 8 GPa are observed around 5 GPa, besides the libron peaks due to the f phase. Furthermore, unknown Raman peaks are also observed at 5-9 GPa. Coexistence of these Raman peaks indicates that the pressure region from 5 to 9 GPa at low temperature does not correspond to a single phase but complicated mixed ones including f and l components.     

Raman scattering and phase changes of CulnSe2 and LiInSe2 at high pressure

Abstract

We have investigated the effect of pressure on the Raman spectra of the ternary chalcogenides CulnSe₂ (chalcopyrite structure) and LiInSe₂ (β-NaFeO₂ structure) for pressures extending well above their first pressure-induced phase transitions. Sign and magnitude of Griineisen parameters are discussed by comparing to related tetrahedrally coordinated chalcogenides. Discontinuous changes of the Raman frequencies indicate pressure-induced phase transitions at 8.0±0.3 and 4.2±0.2 GPa in CuInSe₂ and in LiInSe₂, respectively. The Raman spectra of the low-pressure phases are not recovered after pressure release but a highly disordered structure is induced. In the case of LiInSe₂, the effect of laser heating on the Raman spectra of the high-pressure phase is investigated and discussed in light of recent high-pressure x-ray investigations.     

Structural and crystallization behavior of (Ba,Sr)TiO3 borosilicate glasses

Various glass samples were prepared by melt quench technique in the glass system [(Ba_{1? x} Sr _x ) TiO₃]–[2SiO₂–B₂O₃]–[K₂O] doped with 1?mole% of La₂O₃. Infrared spectra show the number of absorption peaks with different spliting in the wave number range from 450 to 4000?cm^?1. Absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B–O of trigonal BO₃. Raman spectra show the Raman bands due to ring-type metaborate anions, symmetric breathing vibrations BO₃ triangles replaced by BO₄ tetrahedra, and symmetric breathing vibrations of six-member rings. The differential thermal analysis of a glass sample corresponding to composition x?=?0.0 shows crystallization temperature at 847°C and glass transition temperature at 688°C. X-ray diffraction (XRD) pattern of glass ceramic samples shows the major crystalline phase of BaTiO₃ whereas pyrochlore phases of barium titanium silicate. Scanning electron micrographs confirm the results of XRD as barium titanate is major crystalline phase along with pyrochlore phase of barium titanium silicate.     

钛-硅系快速热退火固相反应机制的研究

钛膜在10^-7Torr真空中用电子束蒸发沉积在硅单晶片上,以快速热退火方式进行团相反应。转靶X射线衍射分析发现,540—600℃退火后,有两个亚稳相Ti₅Si₄的衍射峰。延长退火时间,第一成核相Ti₅Si₄可持续存在到钛被消耗完,随即转变成稳定相TiSi₂。退火温度高于640℃,形成稳定相TiSi₂。薄层电阻和喇曼散射的测量研究结果表明,与X射线衍射有很好的对应。207和244cm^-1波数处的两个喇曼峰为TiSi₂的特征喇曼峰,而270,297和341cm^-1的三个喇曼峰似乎是由Ti₅Si₄引起。 关键词：     

Effect of high pressure on raman spectra of T1-based superconducting crystals

Abstract

Raman spectra for two members of the high-Tc superconductor family T1_m Ba₂ Ca₂ cuo_6+m were measured at pressure up to 3 0 GPa. It is shown that pressure induces nonuniform deformation of the unit cell. Analysis of Raman shifts indicates the applicability of a Gruneisen model for these high-Tc superconductors. As evidenced by the absence of changes of the Raman spectra, no phase transitions occur in the pressure range studied.     

新型BCN化合物的结构表征和相转变

将石墨和六方氮化硼(h-BN)混合粉球磨120h形成的非晶B-C-N粉在4.5GPa，1600K等温退火45min. XRD，TEM和Raman散射测量结果表明，高压合成的产物由晶格常数为a₁=0.2551nm，c₁=0.6716nm的六方Ⅰ相和a₂=1.2360nm，c₂=0.8570nm的六方Ⅱ相组成，其中六方Ⅱ相为B-C-N 新相. 在室温该新相在1279，1368，1398cm^-1出现三个特征Raman峰. 变温Raman测量结果表明，在测量温度T=93K时，样品中的主要相为六方Ⅰ相，随着温度的升高，六方Ⅰ相逐渐向六方Ⅱ相转变，当T>473K时，六方Ⅰ相完全转变成六方Ⅱ相. 当温度从673K降到93K过程中，样品又从六方Ⅱ相逐渐变回到六方Ⅰ相. 对这一相变的机理进行了讨论. 关键词： B-C-N 机械球磨 高温高压 相转变     

Low Frequency Raman Spectra of Some Lactams

Abstract

Low frequency Raman spectra from 20 to 200 cm^?1 of δ-valerolactam and ε-caprolactam in CCl₄ solution have been measured at different temperatures (25–80°C). Experimental data were transformed to the R(v) representation and the assignments of some bands are discussed based on measurements of depolarization ratio. The spectral features indicate that C₂ symmetry dimers are predominant. Previous assignments of some bands are also revised.     

Invoking forbidden modes in SnO2 nanoparticles using tip enhanced Raman spectroscopy

Raman forbidden modes and surface defect‐related Raman features in SnO₂ nanostructures carry information about disorder and surface defects which strongly influence important technological applications like catalysis and sensing. Because of the weak intensities of these peaks, it is difficult to identify these features by using conventional Raman spectroscopy. Tip enhanced Raman spectroscopy (TERS) studies conducted on SnO₂ nanoparticles (NPs) of size 4 and 25 nm have offered significant insights of prevalent defects and disorders. Along with one order enhancement in symmetry allowed Raman modes, new peaks related to disorder and surface defects of SnO₂ NPs were found with significant intensity. Temperature‐dependent Raman studies were also carried out for these NPs and correlated with the TERS spectra. For quasi‐quantum dot sized 4‐nm NPs, the TERS study was found to be the best technique to probe the finite size‐related Raman forbidden modes. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermoluminescence of Chromium Doped Cd2Nb2O7 Crystals

The exposure of the Cd₂Nb₂O₇:Cr crystal to monochromatic light with wavelength shorter than 600 nm at 12 K decreases the Cr^3? photoluminescence emission and allows us to observe thermoluminescence within 60–200 K during subsequent heating of the crystal at a rate of 0.077 K/s. The glow curve of thermoluminescence revealed a rather complex structure with two pronounced intensive glow peaks at 91 and 180 K and four rather weak peaks at 99, 117, 132, and 155K. An analysis of the glow peaks by “an initial rise” gave evidence of many various charge carrier traps with activation energies from 150 to 470 meV. Since a comparison of the thermoluminescence and photoluminescence emission spectra showed that these spectra are identical, it was concluded that the thermoluminescence glow peaks are associated with thermal release of charge carriers from shallow traps followed by Cr^4?→Cr^3?(²E) and/or Cr^2?→Cr^3?(²E) charge capture and ²E→⁴A₂ radiative decay of Cr^3?(²E) ions.     

Phase transitions and vibrational study of Rb2SeO4·Te(OH)6 and Rb1.12(NH4)0.88SO4·Te(OH)6

Calorimetry, conductivity, IR and Raman studies of the two ionic-protonic conductors Rb₂SeO₄·Te(OH)₆ (RbSeTe) and Rb_1.12(NH₄)_0.88SO₄·Te(OH)₆ (RNST) have been recorded and analyzed. These compounds crystallize in the monoclinic system, the space groups being, respectively, P2₁/c and P2₁/a for (RbSeTe) and (RNST) with four formula units in their unit cells.

The main feature of these atomic arrangements is the coexistence of two independent and different types of anions in the unit cell, connected by hydrogen bonds, which insure the cohesion of the crystalline edifice. Differential scanning calorimetry traces show three peaks for both the materials, corresponding to three phase transitions, at 430, 470 and 493 K for RbSeTe and at 418, 458 and 483?K for RNST.

A sudden surge in the temperature dependence of conductivity confirms the presence of the third transition, which is characterized by a high conductivity. The Raman spectra of these two materials were investigated in the range 295–600?K and IR spectra achieved at room temperature between 10 and 4000?cm^?1, confirm the presence of the phase transitions and show that anionic groups coexist independently in the same crystal.     

Studies of lattice dynamics in 2HTaS2 by Raman scattering

Raman spectra are presented in the high and low temperature phases of 2H-TaS₂. In the normal phase at 380 K one A_1g- and two E_2g-modes have been observed at 400, 27 and 286 cm^-1, respectively. In the charge density wave state two extra peaks appear with strong scattering intensity in E_2g- symmetry and weak in A_1g-symmetry. The E_2g peak grows and hardens toward 50 cm^-1 with decreasing temperature. The temperature dependence is very similar to the E_2g-mode in 2H-TaSe₂ of similar 3a₀ × 3a₀ superstructure. Other peaks observed in 2H-TaSe₂ in the commensurate phase are not observed. This suggests the incommensurability of the charge density wave state in 2H-TaS₂.     

两原子与双模腔场喇曼相互作用(g1≠g2)的辐射谱

研究了两个有效双能级原子与双模腔场具有不同耦合常数(g₁≠g₂)时通过喇曼相互作用的辐射谱,详细讨论了双模腔场分别处于不同数态时的情形,发现其辐射谱具有如下新特点:当模1腔场处于真空态,模2腔场处于弱场中时,随着R=g₂/g₁的增加,辐射谱交替出现对称的10峰、6峰结构,与单模双原子情形相比较,更为灵敏地反映出两原子与腔场间不同的喇曼相互作用强度;当模1腔场处于真空态、模2腔场处于强场中时,0相似文献   

Dynamic spectral response of solid solutions of the bismuth-strontium ferrite Bi1 − x Sr x FeO3 − δ in the frequency range 0.3–200 THz

Ceramic samples of Bi_{1 ? x} Sr _x FeO_{3 ? δ} have been investigated using X-ray diffraction analysis, Raman spectroscopy, and infrared spectroscopy. It has been shown that the spectra of these solid solutions should be considered as a superposition of resonant phonon responses of the cubic perovskite and a relaxation response. No relaxators are observed in the pure compounds BiFeO₃ and SrFeO_{3 ? δ}. It has been found that two concentration phase transitions occurs with the symmetry changes $R3c \leftrightarrow Pm\bar 3m$ in the range 0.1 < x < 0.2 and $Pm\bar 3m \leftrightarrow P4mm$ in the range 0.8 < x < 1.0.     

The Nanosecond Laser Flash Photolysis (LFP) Transient Spectra of Aqueous CCl4 Solution

Abstract

The Raman spectrum of polycrystalline vaterite is presented and compared to spectra of calcite and aragonite, the other two common CaCO₃ polymorphs; Raman spectroscopy easily distinguishes between these three polymorphs. An important feature of the Raman spectrum of vaterite is splitting of both the ν₁ and ν₄ peaks. The splitting of the ν1 peak implies two distinct site symmetries for the CO₃ ^?2 groups. A definitive crystal structure determination of vaterite is not yet available, but none of the three proposed structures for vaterite show such a feature.     

Synthesis and vibrational spectra of solid solutions based on lanthanum gallate

The synthesis conditions for single-phase solid solutions based on lanthanum gallate, LaGa_{1 ? x} Mg _x O_{3 ? δ}(x= 0–0.25, solid-phase method) and La_{1 ? y}Sr_yGa_{1 ? y}Mg_yO_{3 ? δ}(y= 0–0.2, glycine nitrate method), have been investigated. The structural parameters have been calculated using X-ray powder diffraction data. The IR and Raman spectra have been analyzed. Regularities in the changes in the structural parameters and vibrational spectra with composition are established.     

Unusual "AB" Spectra in High-Resolution Magic-Angle-Spinning NMR-Studies of Solids

Phosphorus-31CP-MAS spectra of Cd(NO₃)₂(PPh₃)₂ have been obtained as a function of spinning frequency. Although the two ³¹P nuclei are crystallographically equivalent and have the same isotropic chemical shifts in the solid state, they exhibit spinning-rate-dependent MAS spectra which have been analyzed to obtain the value of ²J(P, P). At high spinning rates, the spectra are analogous to "A₂" spectra in isotropic solutions, while at slower spinning rates, the spectra are more characteristic of strongly coupled "AB" solution spectra. The AB spectra are unusual in that δ_A = δ_B and J(A, B) is given by the splitting between the alternate peaks in the four-peak multiplet as opposed to the splitting between the outer and adjacent inner lines. This assignment was confirmed by a 2D CP-MAS J-resolved experiment. The unusual spinning-rate-dependent MAS lineshapes result from recoupling of the J interaction between the two crystallographically equivalent nuclei via anisotropic interactions, i.e., weak homonuclear dipolar coupling and differences in the orientation dependence of the chemical-shift tensors. Such spinning-rate-dependent MAS lineshapes are predicted to be a more frequent observation at higher applied magnetic fields.     

Al2O3-Y2O3-ZrO2三相复合陶瓷的介电谱研究

采用传统的固相反应法,在1400–1500 ℃下烧结,制备得到Al₂O₃-Y₂O₃-ZrO₂三相复合陶瓷.样品的结构、形貌和电性能分别用X射线衍射(XRD)、扫描电子显微镜(SEM)及介电谱表征.XRD表明此三相复合体系无其他杂相,加入Y₂O₃及ZrO₂后使得Al₂O₃成瓷温度降低;SEM表明此体系晶粒直径为200–500 nm,并且样品随烧结温度的升高而变得更加致密,晶界更加清晰;介电损耗谱中出现峰值弛豫现象,根据Cole-Cole复阻抗谱得出其为非德拜弛豫. 关键词： 2O₃-Y₂O₃-ZrO₂三相陶瓷')" href="#">Al₂O₃-Y₂O₃-ZrO₂三相陶瓷 介电弛豫 阻抗谱 热导率     

High pressure and low-temperature polymorphism in cyclopentanol

The polymorphism of cyclopentanol (C₅H₁₀O) has been investigated as a function of temperature at ambient pressure and as a function of hydrostatic pressures to 3.7?GPa at room temperature. Differential scanning calorimetry (DSC) and Raman spectra reveal that two plastic phases and two fully ordered crystalline phases are formed during cooling. High pressure Raman and infrared spectra show that cyclopentanol undergoes two-phase transformations. At around 0.6?GPa, the liquid cyclopentanol transforms to a solid plastic structure. On further compression to 1.9?GPa, one fully ordered crystalline phase is observed. Based on pieces of evidence such as peak splitting and emergence of new peaks, it can be concluded that the ordered crystalline structure has a lower symmetry. In addition, the decrease in the wavenumber of the O–H stretching modes at low temperature and high pressure suggests the ordered crystalline phases are characterized by the formation of hydrogen-bonded molecular chains.     

稀土钇、镧掺杂TiO2薄膜的拉曼谱分析

采用溶胶-凝胶法在石英玻璃衬底上用旋涂法制备了未掺杂、掺杂钇和掺杂镧的TiO₂薄膜样品,对样品在700—1100 ℃范围内进行退火处理,并对样品的拉曼光谱进行了分析.分析表明:随着退火温度的升高,未掺杂TiO₂薄膜发生了从锐钛矿相经混相最终向金红石相的转换,掺杂钇和掺杂镧对TiO₂薄膜的晶相转换起阻碍作用,掺杂镧的阻碍作用更强;稀土掺杂能使TiO₂薄膜晶粒细化,并使晶粒内部应力增大从而阻碍晶格振动,掺杂镧比掺杂钇的效果 关键词： 2薄膜')" href="#">TiO₂薄膜 稀土掺杂 拉曼光谱 溶胶-凝胶