Biomolecule-assisted hydrothermal synthesis of Sb2S3 and Bi2S3 nanocrystals and their elevated-temperature oxidation behavior for conversion into α-Sb2O4 and Bi2O3

We have developed a novel biomolecule-assisted hydrothermal method to prepare Sb₂S₃ and Bi₂S₃ nanocrystals with various sizes and shapes, in which cysteine combined with other sulfur source can exert the synergistic effect on products. The samples were characterized XRPD, TEM, HRTEM, FESEM, and PL techniques. First, we prepared a series of Sb₂S₃ and Bi₂S₃ nanocrystals by simply adjusting the composition of sulfur sources under hydrothermal conditions. Then, we studied the elevated-temperature oxidation behavior of these sulfides in air, which can lead to the formation of α-Sb₂O₄ and Bi₂O₃ samples at 600 °C for 3 h. The optical properties of the α-Sb₂O₄ and Bi₂O₃ samples were also discussed.     

Electronic and crystal structure of α- and β-CeIr2Si2

We present the results of XRD, magnetization, resistivity and specific heat measurements of CeIr₂Si₂ single crystals for both, the low-temperature α-phase and the high-temperature β-phase, respectively. The α-phase adopts the tetragonal ThCr₂Si₂-type whereas the β-phase forms in the CaBe₂Ge₂-type structure. Both the phases remain paramagnetic down to low temperatures, nevertheless both, the magnetization and resistivity exhibit pronounced anisotropy in the whole temperature range of measurements (2-300 K). Results of fitting the temperature dependence of the susceptibility within the interconfiguration-fluctuation model point to the Ce valence fluctuating between 3+ and 4+. The α-phase behaves as a Fermi-liquid (FL) at low temperatures whereas the β-phase exhibits non-Fermi-liquid (NFL) features. The results are discussed in context of other similar polymorphic compounds.     

The 2ν1, 2ν2 and 2ν3 overtones of FClO3

The infrared spectra of the 2ν₁, 2ν₂ and 2ν₃ overtones of perchloryl fluoride, FClO₃, have been recorded at high resolution using monoisotopic pure samples. Four symmetric top species have been investigated: F³⁵Cl¹⁶O₃, F³⁷Cl¹⁶O₃, F³⁵Cl¹⁸O₃ and F³⁷Cl¹⁸O₃. The v_i = 2, i = 1, 2, 3 vibrationally excited states are totally symmetric, so these overtones correspond to parallel bands of medium/weak intensity, centered from 2010 to 2120 cm⁻¹ (2ν₁), from 1390 to 1430 cm⁻¹ (2ν₂) and from 1070 to 1100 cm⁻¹ (2ν₃). Most of the bands are unperturbed and their analysis was straightforward. The band origins, the rotational and centrifugal molecular constants in the v₁ = 2, v₂ = 2 and v₃ = 2 states have been determined, with standard deviations of the fits from 0.00024 to 0.00067 cm⁻¹. The 2ν₁ overtones of F³⁵Cl¹⁶O₃ and F³⁷Cl¹⁶O₃ are perturbed by an A₁/E Coriolis resonance between the v₁ = 2 state and one E component of the v₄ = 1, v₆ = 2 manifold. The 2ν₂ of F³⁷Cl¹⁸O₃ is perturbed by the same kind of interaction involving the v₁ = v₆ = 1 (E) state, at about 1396 cm⁻¹. In these bands the resonance is localized on rotational levels with specific J and K values. As a consequence, a few transitions of the perpendicular bands involving the interacting levels could be identified in the spectra. A simultaneous fit of the transitions assigned to the dyads has been performed and the parameters of the excited states have been determined, including the high order Coriolis interaction coefficient . The anharmonic constants x₁₁, x₂₂, x₃₃ of all the studied isotopologues of FClO₃, x₄₆ of F³⁵Cl¹⁶O₃, x₄₆ + g₄₆ of F³⁷Cl¹⁶O₃ and x₁₆ of F³⁷Cl¹⁸O₃, have been derived.     

Rovibrational analysis of the ν2 and 2ν2 P-D stretching bands of PH2D

The infrared spectral regions of the P-D stretching fundamental band ν₂ and the first overtone band 2ν₂ of PH₂D were recorded with a resolution of 2.7×10⁻³ and , respectively. In the analysis about 710 and 440 transitions were assigned to the ν₂ and 2ν₂ bands. These provided 358 and 268 upper rovibrational energy terms, respectively. Resonance interactions between the states (010000) and (000200) were taken into account in the Hamiltonian used to fit upper energies of the (010000) state. The rovibrational energies of the (020000) state were fitted with a Hamiltonian for an isolated vibrational state.     

Fermi-arc superconductivity, pseudogap and charge order in Bi2Sr2CaCu2O8+δ

We report STM/STS observations on the 4a×4a charge order in the pseudogap (PG) and superconducting (SC) states of Bi₂Sr₂CaCu₂O_8+δ, and suggest that the charge order is associated with incoherent quasiparticle or pair states around the antinodal fermi surface (FS), which are also responsible for the PG, and it can coexist with the superconductivity caused by the pairing of coherent quasiparticles on the nodal fermi arc. We also suggest that the nanometer-scale gap inhomogeneity in the SC state, reported previously [Pan, et al., Nature 413 (2001) 282; Mommo, et al., J. Phys. Soc. Jpn. 74 (2005) 2400; Hashimoto, et al., Phys. Rev. B74 (2006) 064508] arises from that in the PG state, which occurs around the antinodal FS.     

DFT calculation of core– and valence–shell electron excitation and ionization energies of 2,1,3-benzothiadiazole C6H4SN2, 1,3,2,4-benzodithiadiazine C6H4S2N2, and 1,3,5,2,4-benzotrithiadiazepine C6H4S3N2

The vertical core– and valence–shell electron excitation and ionization energies of the three title molecules, 1–3, were calculated by density functional theory (DFT) using adequate functional for each type of processes and atoms under study. The inner shells treated were C1s, N1s, S1s, S2s, S2p. Molecular geometry was optimized by DFT B3LYP/6-311 + (d,p). The basis set of triple zeta plus polarization (TZP) Slater-type orbitals was employed for DFT calculations. The ΔSCF method was used to calculate ionization energies. The average absolute deviation (AAD) from experiment of 26 valence-electron ionization energies calculated by DFT for the three molecules 1–3 was 0.14 eV; while that of 24 calculated core-electron binding energies (CEBEs) from experiment was 0.4 eV. Selected core excitation energies were calculated by the multiplet approximation for the three molecules. The AAD of twelve calculated core excitation energies by the multiplet approximation that exclude S2s cases was 0.56 eV. Time-dependent DFT (TDDFT) was employed to calculate the excitation energies and corresponding oscillator strengths of core- and valence-electrons of the molecules. Some selected occupied core orbitals were used to calculate the core-excitation energies with the TDDFT (Sterner–Frozoni–Simone scheme). The core excitation energies thus calculated were in an average error of ca. 28 eV compared to observed values. They were shifted to the value calculated by the multiplet approximation. Convoluted spectra based upon the shifted energies and accompanying oscillator strengths reproduce low-energy region of observed spectra reasonably well, whereas they deviate from experiment in high-energy region. Reasonable agreement between theory and experiment was obtained for the valence electron excitations of the molecules.     

Laser Resistance of Ta2O5/SiO2 and ZrO2/SiO2 Optical Coatings under 2μm Femtosecond Pulsed Irradiation

Ta₂O₅/SiO₂ and ZrO₂/SiO₂ high reflecting (HR) coatings are prepared by ion beam sputtering and electron beam evaporation, respectively. The laser-induced damage thresholds (LIDTs) of these samples are investigated with 2 μm femtosecond pulse lasers (80 fs, 1 kHz). It is found that the Ta₂O₅/SiO₂ HR coating has a higher capability of laser damage resistance than the ZrO₂/SiO₂ HR coating in the 2 μm femtosecond regime. The scanning electron microscope results show that the damage sites of the ZrO₂/SiO₂ HR coating have a relatively porous structure, the loose structure of coatings will provide more sites for water molecules, and the LIDTs of HR coatings will be reduced as a result of the strong water absorption at the wavelength of 2 μm.     

H2O line strengths revisited: ν2 and 2ν2-ν2 at 6 μm

The necessity to revisit water spectroscopy at 6 μm was prompted by recent work indicating that some prior measurements of H₂¹⁶O line strengths (ranging through seven orders of magnitude) had larger than expected systematic errors for the stronger transitions. To investigate this, linestrengths of stronger transitions were re-measured (with 14 new H₂O spectra recorded with a Bruker 125 HR Fourier transform spectrometer at the Jet Propulsion Laboratory) and combined with re-analyzed prior results (obtained at higher optical densities from 32 spectra recorded with the FTS at Kitt Peak). Systematic differences for some of the older data sets were identified and corrected. In this paper, an internally-consistent sampling of 1243 selected line strengths are reported for (0 1 0)-(0 0 0) and (0 2 0)-(0 1 0) transitions between 783 and 2378 cm⁻¹. To confirm experimental precisions, observed and calculated line strengths are compared.     

N2 and O2 pressure broadening and pressure shift in the 4ν2 band of OCS

To measure accurately OCS concentrations in planetary atmospheres, it is important to know precisely nitrogen and oxygen pressure broadening and pressure-induced shift coefficients for the lines used in the retrievals. We present in this study the corresponding coefficients for lines of the P and R branches of the 4ν₂ band of the primary isotopologue of carbonyl sulfide (¹⁶O¹²C³²S).For this purpose, infrared absorption spectra of a natural carbonyl sulfide (OCS) gas sample were recorded at an unapodized resolution of 0.004 cm⁻¹, at room temperature for different pressures of N₂ and O₂, using a Bruker IFS125HR spectrometer at the LISA Laboratory in France. The line parameters were derived using the multispectrum fitting method applied to the measured shapes of the lines, including the interference effects caused by the line overlaps.The results are compared with earlier measurements and with values calculated using a semi-classical model based upon the Robert and Bonamy formalism that reproduces rather well the experimental m (m=−J for P(J) lines and m=J+1 for R(J) lines) quantum number dependence of the N₂ and O₂ broadening coefficients. On the other hand most of the lines studied here have positive shift coefficients, which do not show any systematic dependence on m. However, in previous studies of the ν₃, 2ν₃ and ν₂ bands, these coefficients were negative for all lines.     

Varistor and dielectric properties of Cr2O3 doped SnO2–Zn2SnO4 composite ceramics

Cr₂O₃ doped SnO₂–Zn₂SnO₄ composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Cr₂O₃ content, the breakdown electrical field E_B increases from 11 to 92 V/mm and the relative dielectric constant ε_r measured at 1 kHz, 50 °C decreases from 11,028 to 3412, respectively. The barrier height ?_B about 0.8–0.84 eV and the decreasing of SnO₂ grain size suggest that the varistor behavior with high ε_r is originated from SnO₂–SnO₂ or SnO₂–Zn₂SnO₄ grain boundary. In the dielectric spectra lower than 1 kHz, a dielectric peak is presented and depressed with increasing bias voltage. Similarly, at high temperature, the dielectric constant also presents a dielectric peak in the temperature spectra and the peak becomes faint with increasing frequency. The exhibition of the dielectric peak is thought to be attributed to the conduction of grain boundary since it is accompanied by the sharp increase of dielectric loss. In addition, a dielectric relaxation with the activation energy about 0.4–0.5 eV was observed in the temperature range of 20–100 °C. Based on the results, the formation mechanism of Schottky barriers at grain boundaries and the varistor behavior with high dielectric constant are well understood.     

Vibration-rotation and deperturbation analysis of A2Π-X2Σ+ and B2Σ+-X2Σ+ systems of the CaI molecule

Doppler-limited laser excitation spectroscopy employing narrow-band fluorescence detection was used to obtain a rotational and vibrational analysis in the (0, 0) and (1, 1) bands of the A²Π-X²Σ⁺ system and the (4, 2) (3, 1), (0, 0), (0, 1), (1, 2), (2, 3), and (3, 4) bands of the B²Σ⁺-X²Σ⁺ system of CaI. The A and B states are deperturbed to obtain spectroscopic constants and Franck-Condon factors. Deperturbation was necessary because of the small separation of the A and B states relative to the A ～ B interaction strength and the A²Π spin-orbit splitting. The main deperturbed constants (in cm^?1) are

     

12.

Electronic and thermodynamic properties of α-Pu₂O₃     

Yong Lu  Yu Yang  Fawei Zheng  Ping Zhang 《Physics letters. A》2014

Based on density functional theory+U$\text{density functional theory}+U$ calculations and the quasi-annealing simulation method, we obtain the ground electronic state for α-Pu₂O₃ and present its phonon dispersion curves as well as various thermodynamic properties, which have seldom been theoretically studied because of the huge unit cell. We find that the Pu–O chemical bonding is weaker in α-Pu₂O₃ than in fluorite PuO₂, and subsequently a frequency gap appears between oxygen and plutonium vibration density of states. Based on the calculated Helmholtz free energies at different temperatures, we further study the reaction energies for Pu oxidation, PuO₂ reduction, and transformation between PuO₂ and α-Pu₂O₃. Our reaction energy results are in agreements with available experiment. And it is revealed that high temperature and insufficient oxygen environment are in favor of the formation of α-Pu₂O₃.     

13.

Bi₂Pb₂V₂O₁₀的晶体结构          下载免费PDF全文

王佩玲  李德宇 《物理学报》1985,34(2):235-240

使用X射线单晶衍射法测定了Bi₂Pb₂V₂O₁₀的结构。该晶体属三斜晶系,空间群为C₁¹-P1,单位晶胞内化学式数Z=1,晶胞参数为:a=7.084(4)?,b=7.278(3)?,c=5.587(3)?,α=111.91(5)°,β=95.01(6)°,γ=108.86(4)°,V=245.70?³,D_x=7.35g/cm³,μ(MoK_α)=678,94cm^-1,F(000)=456。用Patterson函数分析及Forier技术测定了结构,对原子坐标、各向同性及各向异性热参数进行了最小二乘方修正,R=0.079。结构分析表明,Bi₂Pb₂V₂O₁₀的Pb原子与O原子形成八角十二面体,Bi原子与O原子形成六角多面体。两个共棱的Pb—O多面体与两个共棱的Bi—O多面体相连,并沿bc平面无限延伸。讨论了吸收的影响。最后,将Bi₂Pb₂VO₁₀的结构与Pb₂SO₅的结构进行了比较。 关键词：     

14.

Magnetic,magnetoelectric and dielectric behavior of CoFe₂O₄–Pb(Fe_1/2Nb_1/2)O₃ particulate and layered composites     

J. Kulawik  D. SzwagierczakP. Guzdek 《Journal of magnetism and magnetic materials》2012

Magnetic, magnetoelectric and dielectric properties of multiferroic CoFe₂O₄–Pb(Fe_1/2Nb_1/2)O₃ composites prepared as bulk ceramics were compared with those of tape cast and cofired laminates consisting of alternate ferrite and relaxor layers. X-ray diffraction analysis and Scanning Electron Microscope observations of ceramic samples revealed two-phase composition and fine grained microstructure with uniformly distributed ferrite and relaxor phases. High and broad maxima of dielectric permittivity attributed to dielectric relaxation were found for ceramic samples measured in a temperature range from −55 to 500 °C at frequencies 10 Hz–2 MHz. Magnetic hysteresis, zero-field cooled (ZFC) and field cooled (FC) curves, and dependencies of magnetization on temperature for both magnetoelectric composites were measured with a vibrating sample magnetometer in an applied magnetic field up to 80 kOe at 4–400 K. The hysteresis loops obtained for composites are typical of a mixture of the hard magnetic material with a significant amount of the paramagnet. The bifurcation of ZFC–FC magnetizations observed for both composites implies spin-glass behavior. Magnetoelectric properties at room temperature were investigated as a function of dc magnetic field (0.3–7.2 kOe) and frequency (10 Hz–10 kHz) of ac magnetic field. Both types of composites exhibit a distinct magnetoelectric effect. Maximum values of magnetoelectric coefficient attained for the layered composites exceed 200 mV/(cm Oe) and are almost three times higher than those for particulate composites.     

15.

Porous silicon based β-FeSi₂ and photoluminescence     

H. T. Chen  X. L. Wu  Y. Y. Zhang  W. N. Su 《Applied Physics A: Materials Science & Processing》2009,97(3):725-728

Highly-pure iron powder was covered on porous silicon for fabricating semiconducting β-FeSi₂ structures. X-ray diffraction and Raman scattering results confirm the formation of pure-phase β-FeSi₂ after high-temperature annealing at 1100°C and then long-time persistence at 900°C. Scanning electron microscope observations reveal that large-size (>μm) β-FeSi₂ grains mainly form in the pores of porous silicon and some nanocrystals grow on local surfaces. The temperature-dependent photoluminescence spectra disclose that the observed ∼1.54 μm emission arises from free exciton recombination, which is confirmed via the activation energy (0.25 eV) measurement. Our method provides a way to synthesize single-phase β-FeSi₂ materials.     

16.

Magnetic and structural properties of CaO–SiO₂–P₂O₅–Na₂O–Fe₂O₃ glass ceramics     

Rajendra Kumar Singh  G.P. Kothiyal  A. Srinivasan 《Journal of magnetism and magnetic materials》2008

Magnetic properties of glass ceramics derived from glasses with composition 41CaO·(52−x)SiO₂·4P₂O₅·xFe₂O₃·3Na₂O (2?x?10 mol% iron oxide (Fe₂O₃)) are reported. Structural investigation revealed the presence of nanocrystalline magnetite phase in the heat-treated samples containing x?2 mol% Fe₂O₃. Magnetic hysteresis cycles of the glass-ceramic samples were obtained with a maximum applied field of ±20 kOe as well as a low field of ±500 Oe, in order to evaluate the potential of these glass ceramics for hyperthermia treatment of cancer. Samples with x>2 mol% of iron oxide exhibited magnetic behavior similar to soft magnetic materials with low coercivity. The evolution of magnetic properties in these samples as a function of iron oxide molar concentration is correlated with the amount and crystallite size of magnetite phase present in them.     

17.

Enhanced 1.53-μm and lowered upconversion luminescence in Er-doped Ga₂O₃-GeO₂-Bi₂O₃-Na₂O glass by codoping rare earths     

D.M. Shi  Y.G. ZhaoX.F. Wang 《Physica B: Condensed Matter》2011,406(13):2588-2593

Spectroscopic properties and energy transfer (ET) in Ga₂O₃-GeO₂-Bi₂O₃-Na₂O (GGBN, glass doped with Er³⁺ and rare earths (RE³⁺; RE³⁺=Ce³⁺, Tb³⁺) have been investigated. Intense 1.53-μm emission with the peak emission cross-section achieved to 7.58×10⁻²¹ cm² from Er³⁺-doped GGBN glass has been obtained upon excitation at 980 nm. Effects of RE³⁺ (RE³⁺=Ce³⁺, Tb³⁺) codoping on the optical properties of Er³⁺-doped GGBN glass have been investigated and the possible ET mechanisms involved have also been discussed. Significant enhancement of the 1.53 μm emission intensity and decrease of upconversion (UC) fluorescence with increasing Ce³⁺ concentration have been observed. The incorporation of Tb³⁺ into Er³⁺-doped GGBN glass could significantly decrease the UC emission intensity, but meanwhile decrease the 1.53 μm emission intensity due to the ET from Er³⁺:⁴I_13/2 to Tb³⁺:⁷F₂. The results indicate that the incorporation of Ce³⁺ into Er³⁺-doped GGBN glass can effectively improve 1.53-μm and lower UC luminescence, which makes GGBN glass more attractive for use in C-band optical fiber amplifiers.     

18.

Infrared spectra of two isomers of OCS-C₂H₂ and OCS-C₂D₂ in the region of OCS ν₁ fundamental     

J. Norooz Oliaee  M. Dehghany  A.R.W. McKellar 《Journal of Molecular Spectroscopy》2009,257(2):133-10422

Infrared spectra of OCS-C₂H₂ and OCS-C₂D₂ complexes in the region of the C-O stretching fundamental of OCS (∼2060 cm⁻¹) are studied in a pulsed supersonic slit-jet expansion using a tunable diode laser. For each complex, two bands are observed and assigned to distinct near-parallel and the T-shaped isomers. Ground state parameters were previously determined from microwave studies, so analysis of the infrared spectra gives information on the vibrational shifts upon complex formation as well as rotational and centrifugal distortion parameters for the excited states. All four bands show a red shift with respect to the monomer band origin, with the T-shaped isomer having a much larger shift than the near-parallel isomer. Disappearance of the T-shaped isomer when argon is used as a carrier gas supports the notion that the near-parallel isomer is the lowest energy form of the complex.     

19.

Line shifts in the ν₂, 2ν₂, and ν₄ bands of NH₃ perturbed by O₂     

H. Aroui  P. Chelin  C.E. Fellows  J. Orphal 《Journal of Molecular Spectroscopy》2008,252(2):129-135

Pressure-induced line shift coefficients have been measured for more than 200 rovibrational lines of NH₃ perturbed by O₂ at room temperature (T = 295 K) in some branches of the ν₂, 2ν₂, and ν₄ bands. These lines with J values ranging from 1 to 13 are located in the spectral range 800-1800 cm⁻¹. Experiments were made with a high-resolution Fourier transform spectrometer. The treatment of vibration-rotation lines includes interference effects caused by the overlapping of lines. The O₂ pressure-induced shift coefficients have been derived from the non-linear least-squares multi-pressure fitting technique. The results illustrate a vibrational dependence of line shifts with vibrational quantum number. Most of the measured shifts are negative in the ν₄ band. They are positive for the ν₂ and 2ν₂ bands. The measured shift coefficients are compared with previous measurements and with those calculated from a semiclassical theory based upon the Robert-Bonamy formalism extended to the case of symmetric top molecule with inversion motion. The predictions are generally in satisfactory agreement with the experimental data. Analyses of measured and predicted results illustrate that these shifts mainly originate from the isotropic part of the intermolecular potential.     

20.

BaO-Li₂O-B₂O₃三元系中BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O截面相平衡关系的研究          下载免费PDF全文

黄清镇  王国富  梁敬魁 《物理学报》1984,33(1):76-85

本文用X射线和差热分析方法对BaO-Li₂O-B₂O₃三元系中的两个截面:BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O作了研究。在BaB₂O₄-Li₂B₂O₄赝二元系中发现了一个新的化合物4BaB₂O₄·Li₂B₂O₄。化合物在930±3℃由包晶反应形成,并与Li₂B₂O₄形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol％Li₂B₂O₄。在BaB₂O₄-Li₂O截面中也存在化合物4BaB₂O₄·Li₂B₂O₄,其包晶反应温度从930±3℃随Li₂O含量增加下降到908±3℃。在组分60mol％Li₂O处形成另一个新的化合物2BaB₂O₄·3Li₂O。该化合物在630±3℃也是由包晶反应形成,并与Li₂O和Li₂CO₃分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB₂O₄·Li₂B₂O₄和2BaB₂O₄·3Li₂O的X射线粉末衍射图案进行了指标化,其结果:4BaB₂O₄·Li₂B₂O₄的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB₂O₄·3Li₂O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。 关键词：     

	$\text{X}{}^2\text{Σ}{}^{\mathrm{+}}$	$\text{A}{}^2\text{Π}$	$\text{B}{}^2\text{Σ}{}^{\mathrm{+}}$
$\text{T}{}_{\mathrm{e}}$	0	15 624.67(5)	15 700.52(12)
$\text{ω}{}_{\mathrm{e}}$	238.7496(33)	241.19(7)	242.63(17)
$\text{ω}{}_{\mathrm{e}}\text{χ}{}_{\mathrm{e}}$	0.62789(64)	0.53(5) (Pekeris)	1.17(12) (Pekeris)
$\text{B}{}_{\mathrm{e}}$	0.0693254(84)	0.070460(14)	0.071572(22)
$\text{α}{}_{\mathrm{e}}\text{× 10}{}^4$	2.640(35)	2.15(10)	3.95(2)
$\text{A}{}_{\mathrm{e}}$	—	45.8968(52)	—
$\text{R}{}_{\mathrm{e}}\text{(}\text{A}\text{?}\text{)}$	2.8286(2)	2.8057(3)	2.7839(4)

Electronic and thermodynamic properties of α-Pu2O3

Based on density functional theory+U$\text{density functional theory}+U$ calculations and the quasi-annealing simulation method, we obtain the ground electronic state for α-Pu₂O₃ and present its phonon dispersion curves as well as various thermodynamic properties, which have seldom been theoretically studied because of the huge unit cell. We find that the Pu–O chemical bonding is weaker in α-Pu₂O₃ than in fluorite PuO₂, and subsequently a frequency gap appears between oxygen and plutonium vibration density of states. Based on the calculated Helmholtz free energies at different temperatures, we further study the reaction energies for Pu oxidation, PuO₂ reduction, and transformation between PuO₂ and α-Pu₂O₃. Our reaction energy results are in agreements with available experiment. And it is revealed that high temperature and insufficient oxygen environment are in favor of the formation of α-Pu₂O₃.     

Bi2Pb2V2O10的晶体结构

使用X射线单晶衍射法测定了Bi₂Pb₂V₂O₁₀的结构。该晶体属三斜晶系,空间群为C₁¹-P1,单位晶胞内化学式数Z=1,晶胞参数为:a=7.084(4)?,b=7.278(3)?,c=5.587(3)?,α=111.91(5)°,β=95.01(6)°,γ=108.86(4)°,V=245.70?³,D_x=7.35g/cm³,μ(MoK_α)=678,94cm^-1,F(000)=456。用Patterson函数分析及Forier技术测定了结构,对原子坐标、各向同性及各向异性热参数进行了最小二乘方修正,R=0.079。结构分析表明,Bi₂Pb₂V₂O₁₀的Pb原子与O原子形成八角十二面体,Bi原子与O原子形成六角多面体。两个共棱的Pb—O多面体与两个共棱的Bi—O多面体相连,并沿bc平面无限延伸。讨论了吸收的影响。最后,将Bi₂Pb₂VO₁₀的结构与Pb₂SO₅的结构进行了比较。 关键词：     

Magnetic,magnetoelectric and dielectric behavior of CoFe2O4–Pb(Fe1/2Nb1/2)O3 particulate and layered composites

Magnetic, magnetoelectric and dielectric properties of multiferroic CoFe₂O₄–Pb(Fe_1/2Nb_1/2)O₃ composites prepared as bulk ceramics were compared with those of tape cast and cofired laminates consisting of alternate ferrite and relaxor layers. X-ray diffraction analysis and Scanning Electron Microscope observations of ceramic samples revealed two-phase composition and fine grained microstructure with uniformly distributed ferrite and relaxor phases. High and broad maxima of dielectric permittivity attributed to dielectric relaxation were found for ceramic samples measured in a temperature range from −55 to 500 °C at frequencies 10 Hz–2 MHz. Magnetic hysteresis, zero-field cooled (ZFC) and field cooled (FC) curves, and dependencies of magnetization on temperature for both magnetoelectric composites were measured with a vibrating sample magnetometer in an applied magnetic field up to 80 kOe at 4–400 K. The hysteresis loops obtained for composites are typical of a mixture of the hard magnetic material with a significant amount of the paramagnet. The bifurcation of ZFC–FC magnetizations observed for both composites implies spin-glass behavior. Magnetoelectric properties at room temperature were investigated as a function of dc magnetic field (0.3–7.2 kOe) and frequency (10 Hz–10 kHz) of ac magnetic field. Both types of composites exhibit a distinct magnetoelectric effect. Maximum values of magnetoelectric coefficient attained for the layered composites exceed 200 mV/(cm Oe) and are almost three times higher than those for particulate composites.     

Porous silicon based β-FeSi2 and photoluminescence

Highly-pure iron powder was covered on porous silicon for fabricating semiconducting β-FeSi₂ structures. X-ray diffraction and Raman scattering results confirm the formation of pure-phase β-FeSi₂ after high-temperature annealing at 1100°C and then long-time persistence at 900°C. Scanning electron microscope observations reveal that large-size (>μm) β-FeSi₂ grains mainly form in the pores of porous silicon and some nanocrystals grow on local surfaces. The temperature-dependent photoluminescence spectra disclose that the observed ∼1.54 μm emission arises from free exciton recombination, which is confirmed via the activation energy (0.25 eV) measurement. Our method provides a way to synthesize single-phase β-FeSi₂ materials.     

Magnetic and structural properties of CaO–SiO2–P2O5–Na2O–Fe2O3 glass ceramics

Magnetic properties of glass ceramics derived from glasses with composition 41CaO·(52−x)SiO₂·4P₂O₅·xFe₂O₃·3Na₂O (2?x?10 mol% iron oxide (Fe₂O₃)) are reported. Structural investigation revealed the presence of nanocrystalline magnetite phase in the heat-treated samples containing x?2 mol% Fe₂O₃. Magnetic hysteresis cycles of the glass-ceramic samples were obtained with a maximum applied field of ±20 kOe as well as a low field of ±500 Oe, in order to evaluate the potential of these glass ceramics for hyperthermia treatment of cancer. Samples with x>2 mol% of iron oxide exhibited magnetic behavior similar to soft magnetic materials with low coercivity. The evolution of magnetic properties in these samples as a function of iron oxide molar concentration is correlated with the amount and crystallite size of magnetite phase present in them.     

Enhanced 1.53-μm and lowered upconversion luminescence in Er-doped Ga2O3-GeO2-Bi2O3-Na2O glass by codoping rare earths

Spectroscopic properties and energy transfer (ET) in Ga₂O₃-GeO₂-Bi₂O₃-Na₂O (GGBN, glass doped with Er³⁺ and rare earths (RE³⁺; RE³⁺=Ce³⁺, Tb³⁺) have been investigated. Intense 1.53-μm emission with the peak emission cross-section achieved to 7.58×10⁻²¹ cm² from Er³⁺-doped GGBN glass has been obtained upon excitation at 980 nm. Effects of RE³⁺ (RE³⁺=Ce³⁺, Tb³⁺) codoping on the optical properties of Er³⁺-doped GGBN glass have been investigated and the possible ET mechanisms involved have also been discussed. Significant enhancement of the 1.53 μm emission intensity and decrease of upconversion (UC) fluorescence with increasing Ce³⁺ concentration have been observed. The incorporation of Tb³⁺ into Er³⁺-doped GGBN glass could significantly decrease the UC emission intensity, but meanwhile decrease the 1.53 μm emission intensity due to the ET from Er³⁺:⁴I_13/2 to Tb³⁺:⁷F₂. The results indicate that the incorporation of Ce³⁺ into Er³⁺-doped GGBN glass can effectively improve 1.53-μm and lower UC luminescence, which makes GGBN glass more attractive for use in C-band optical fiber amplifiers.     

Infrared spectra of two isomers of OCS-C2H2 and OCS-C2D2 in the region of OCS ν1 fundamental

Infrared spectra of OCS-C₂H₂ and OCS-C₂D₂ complexes in the region of the C-O stretching fundamental of OCS (∼2060 cm⁻¹) are studied in a pulsed supersonic slit-jet expansion using a tunable diode laser. For each complex, two bands are observed and assigned to distinct near-parallel and the T-shaped isomers. Ground state parameters were previously determined from microwave studies, so analysis of the infrared spectra gives information on the vibrational shifts upon complex formation as well as rotational and centrifugal distortion parameters for the excited states. All four bands show a red shift with respect to the monomer band origin, with the T-shaped isomer having a much larger shift than the near-parallel isomer. Disappearance of the T-shaped isomer when argon is used as a carrier gas supports the notion that the near-parallel isomer is the lowest energy form of the complex.     

Line shifts in the ν2, 2ν2, and ν4 bands of NH3 perturbed by O2

Pressure-induced line shift coefficients have been measured for more than 200 rovibrational lines of NH₃ perturbed by O₂ at room temperature (T = 295 K) in some branches of the ν₂, 2ν₂, and ν₄ bands. These lines with J values ranging from 1 to 13 are located in the spectral range 800-1800 cm⁻¹. Experiments were made with a high-resolution Fourier transform spectrometer. The treatment of vibration-rotation lines includes interference effects caused by the overlapping of lines. The O₂ pressure-induced shift coefficients have been derived from the non-linear least-squares multi-pressure fitting technique. The results illustrate a vibrational dependence of line shifts with vibrational quantum number. Most of the measured shifts are negative in the ν₄ band. They are positive for the ν₂ and 2ν₂ bands. The measured shift coefficients are compared with previous measurements and with those calculated from a semiclassical theory based upon the Robert-Bonamy formalism extended to the case of symmetric top molecule with inversion motion. The predictions are generally in satisfactory agreement with the experimental data. Analyses of measured and predicted results illustrate that these shifts mainly originate from the isotropic part of the intermolecular potential.     

BaO-Li2O-B2O3三元系中BaB2O4-Li2B2O4和BaB2O4-Li2O截面相平衡关系的研究

本文用X射线和差热分析方法对BaO-Li₂O-B₂O₃三元系中的两个截面:BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O作了研究。在BaB₂O₄-Li₂B₂O₄赝二元系中发现了一个新的化合物4BaB₂O₄·Li₂B₂O₄。化合物在930±3℃由包晶反应形成,并与Li₂B₂O₄形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol％Li₂B₂O₄。在BaB₂O₄-Li₂O截面中也存在化合物4BaB₂O₄·Li₂B₂O₄,其包晶反应温度从930±3℃随Li₂O含量增加下降到908±3℃。在组分60mol％Li₂O处形成另一个新的化合物2BaB₂O₄·3Li₂O。该化合物在630±3℃也是由包晶反应形成,并与Li₂O和Li₂CO₃分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB₂O₄-Li₂B₂O₄和BaB₂O₄-Li₂O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB₂O₄·Li₂B₂O₄和2BaB₂O₄·3Li₂O的X射线粉末衍射图案进行了指标化,其结果:4BaB₂O₄·Li₂B₂O₄的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB₂O₄·3Li₂O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。 关键词：