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1.
Compositional behavior of Urbach absorption edge is studied as well as the effect of compositional disordering on the parameters of exciton-phonon interaction, phase transition temperatures and electric conductivity in Cu6P(S1−xSex)5Br1−yIy superionic solid solutions. The effect of different types of disordering on the optical absorption processes and specific features of compositional changes in the absorption edge spectra under S→Se and Br→I anion substitution in the mixed crystals are investigated. (x, T) phase diagrams for Cu6P(S1−xSex)5X (X=I, Br) solid solutions are studied. 相似文献
2.
I.P. Studenyak O.P. Kokhan V.V. Bilanchuk 《Journal of Physics and Chemistry of Solids》2007,68(10):1881-1884
Phase diagram of Cu7GeS5I-Cu7GeSe5I superionic system was investigated by the differential thermal analysis (DTA). Chemical interaction in Cu7GeS5I-Cu7GeSe5I system was studied by X-ray phase analysis (XPA), microstructural analysis, and density determination. Compositional behaviour of diffuse reflection spectra and energy gap due to S→Se anion substitution in Cu7Ge(S1−xSex)5I solid solutions are discussed. 相似文献
3.
M. Kranj?ec I.P. Studenyak V.S. Dyordyay 《Journal of Physics and Chemistry of Solids》2004,65(5):1015-1020
Temperature behaviour of optical absorption edge in Cu6PS5I1−xBrx mixed crystals is studied in the interval 77-325 K. It is shown that the absorption edge has Urbach shape in the 215-325 K temperature interval. The influence of temperature and compositional disorder on the Urbach absorption edge parameters is presented. The mechanism of the Urbach bundle formation and the effect of I→Br anionic substitution on the exciton-phonon interaction parameters is elucidated. 相似文献
4.
I.P. Studenyak M.I. Kayla M. Kranj?ec O.P. Kokhan Yu.V. Minets 《Journal of Physics and Chemistry of Solids》2011,72(12):1419-1422
Cu6AsS5I single crystals were grown using chemical vapour transport method. Two low-temperature phase transitions (PT) are observed from isoabsorption studies: a first-order PT at Т?=153±1 K and a second-order PT in the temperature interval T?I=260–280 K. At low temperatures and high absorption levels an excitonic absorption band was revealed in the range of direct optical transitions. At Т>Т?, the absorption edge has an exponential shape and a characteristic Urbach bundle is observed. The influence of the cationic P→As substitution on the parameters of the Urbach absorption edge, parameters of exciton–phonon interaction, and phase transitions temperatures are studied. 相似文献
5.
K.D. Setzer 《Journal of Molecular Spectroscopy》2006,236(2):224-233
Emission spectra of the b1Σ+(b0+) → X3Σ−(X10+,X21) and a1Δ(a2) → X21 transitions of AsBr have been measured in the near-infrared spectral region with a Fourier-transform spectrometer. The arsenic bromide radicals were generated in fast-flow systems by reaction of arsenic vapor (Asx) with bromine and were excited by microwave-discharged oxygen. The most prominent features in the spectrum are the Δv = +1,0,−1, and −2 band sequences of the b1Σ+(b0+) → X3Σ−(X10+) transition in the range 11 700-12 700 cm−1. With lower intensities, the Δv = 0 and −1 sequences of the b1Σ+(b0+) → X3Σ−(X21) sub-system show up in the same range. Further to the red, between 6000 and 6700 cm−1, the Δv = 0, +1, and −1 sequences of the hitherto unknown a1Δ(a2) → X21 transition are observed. Analyses of medium- and high-resolution spectra have yielded improved molecular constants for the X10+, X21, and b0+ states and first values of the electronic energy and the vibrational constants of the a2 state. 相似文献
6.
N.M. Gasanly 《Physica B: Condensed Matter》2012,407(21):4318-4322
The absorption edge of undoped Tl2Ga2S3Se crystals have been studied through transmission and reflection measurements in the wavelength range 440–1100 nm and in the temperature range 10–300 K. The absorption edge was observed to shift toward lower energy values with increasing temperature. As a result, the rate of the indirect band gap variation with temperature γ=−2.6×10−4 eV/K and the absolute zero value of the band gap energy Egi(0)=2.42 eV were obtained. 相似文献
7.
I.P. Studenyak M. Kranj?ec V.V. Bilanchuk O.P Kokhan A.F. Orliukas A. Kezionis E. Kazakevicius T. Salkus 《Journal of Physics and Chemistry of Solids》2009,70(12):1478-1481
Single crystals of Cu7GeSe5I superionic conductor were grown by chemical transport. Their electrical conductivity in the frequency range 1.0×106–1.2×109 Hz and in the temperature range 196–295 K was measured. Cu7GeSe5I crystal is shown to exhibit a rather high electrical conductivity (σ295=64.0 S/m at 295 K) and a low activation energy (ΔEa=0.125 eV). Optical absorption edge of Cu7GeSe5I crystals in the temperature range 77–300 K was studied, the temperature dependences of the optical pseudogap and Urbach energy being obtained. The effect of different types of disordering on the Urbach absorption edge and electron–phonon interaction parameters was investigated. 相似文献
8.
I.P. Studenyak V.Yu. Izai V.V. Panko A. Plecenik 《Journal of Physics and Chemistry of Solids》2010,71(7):988-992
Cu6PS5I superionic crystals, grown using chemical vapour transport, were implanted by sulphur ions. The ion implantation effect on the phase transitions is studied by temperature isoabsorption investigation of the optical absorption edge. For the implanted crystals the optical absorption edge shape is studied in the temperature range 77-320 K, the parameters of exciton-phonon interaction, resulting in the Urbach behaviour of the optical absorption edge, are determined, the temperature dependences of the optical pseudogap and Urbach energy are obtained. The implantation effect on the ordering-disordering processes in Cu6PS5I superionic conductors is studied. 相似文献
9.
Series of polycrystalline samples of Zn2−xCuxBaFe16O27 were prepared by usual ceramic methods, where x=0.0, 0.4, 0.6, 0.8, 1.0, 1.4. X-ray analysis done at room temperature using CoKα with λ=1.790 Å confirms the presence of W-type hexaferrite phase structure. Saturation magnetization and hysteresis loops curves measurements at room temperature were studied as a function of Cu2+ substitution. It can be seen that the Cu2+ content slightly decreases the saturation magnetization from 25 to 20 emu g−1; all hysteresis loops are closed, which indicates low anisotropy field and low saturation magnetization field. The dc conductivity and thermoelectric power were measured in a range from room temperature up to T=750 K for all samples. The thermoelectric power decreases on increasing Cu2+ content, and the conductivity increases with temperature. The value of the charge-carrier concentration increases by increasing the temperature and Cu2+ content. 相似文献
10.
K.D. Setzer 《Journal of Molecular Spectroscopy》2003,221(1):19-22
Emission spectra of the b1Σ+(b0+)→X3Σ−(X10+) transition of phosphorus iodide have been measured with a high-resolution Fourier-transform spectrometer. The PI radicals were generated and excited in a fast-flow system by reaction of phosphorus vapor (Px) with iodine and microwave-discharged oxygen. Four sequences, Δv=0,+1,−1,−2, of the b1Σ+(b0+)→X3Σ−(X10+) transition of PI comprising 28 bands were observed. Six bands were measured at high spectral resolution. Vibrational and rotational analyses have yielded accurate spectroscopic constants of the X10+ and b0+ states (in cm−1): X10+: ωe=371.296(4), ωexe=1.3302(9), Be=0.1194117(2), αB=−0.0005676(7), De=4.56(2) ×10−8; b0+: Te=11136.921(4), ωe=400.165(6), ωexe=1.345(2), Be=0.1239237(2), αB=−0.0005540(2), De=4.84(5) × 10−8, where the numbers in parentheses are the standard deviations of the parameters. No emissions of the b0+→X21 sub-system nor of the a1Δ(a2)→X3Σ−(X21) transition have been observed leaving PI the only group Va halide for which the spin splitting in the X3Σ− ground state is still unknown. 相似文献
11.
Zeng LuTang Wanjun 《Physica B: Condensed Matter》2011,406(14):2901-2903
A series of NaY1−yEuy(WO4)2−x(MoO4)x (x=0−2 and y=0.06−0.15) phosphors have been prepared by a combustion route. X-ray powder diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The excitation spectra of these phosphors show the strongest absorption at about 396 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show an intense red emission at 616 nm due to the 5D0→7F2 electric dipole transition of Eu3+. As the Mo content increases, the intensity of the 5D0→7F2 emission of Eu3+ activated at wavelength of 396 nm increases and reaches a maximum when the relative ratio of Mo/W is 2:3. The intense red-emission of the tungstomolybdate phosphors at near-UV excitation suggests that the material is a potential candidate for white light emitting diode (WLEDs). 相似文献
12.
Yunfeng Bai 《Optics Communications》2009,282(9):1922-1928
Er/Tm/Yb codoped Y2O3 nanocrystals and Er/Tm/Yb/Li codoped Y2O3 nanocrystals have been synthesized by sol-gel method, bright white light emission has been observed at 976 nm excitation. The blue, green, and red emissions, respectively, arise from the transitions 1G4 → 3H6 of Tm3+, 2H11/2/4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of Er3+ ion. Moreover, after doping Li+ ions into Er/Tm/Yb codoped Y2O3 nanocrystals, the white light emission increase greatly. CIE coordinate of Er/Tm/Yb/Li codoped Y2O3 nanocrystals is X = 0.32 and Y = 0.36 at 10 W/cm2 excitation, which is very close to the standard equal energy white light illuminate (X = 0.33, Y = 0.33). 相似文献
13.
Xiuai Lu Zhenyu You Zhaojie Zhu Baichang Wu 《Journal of Physics and Chemistry of Solids》2005,66(10):1801-1805
Dy3+: Ca3(BO3)2 crystal was grown successfully by the Czochraski technique. The absorption spectrum was measured and its absorption peaks were assigned. The Judd-Ofelt intensity parameters were found to be Ω2=5.216×10−20, Ω4=1.858×10−20, Ω6=0.623×10−20 cm2. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated. Also, room temperature luminescence decay curve in correspondence with the emission line 4F9/2→6H13/2 centered at 575 nm was measured. 相似文献
14.
H. Peng C.L. Wang J.C. Li R.Z. Zhang M.X. Wang H.C. Wang Y. Sun M. Sheng 《Physics letters. A》2010,374(36):3797-3800
First principle calculations have been performed to study the lattice vibration of BaX2 (X = Si, Ge). A rigid-unit vibrational mode has been observed, and this mode confines and scatters acoustic phonon modes, leading to a low thermal conductivity. Their stability is analyzed from the calculations of thermodynamic properties. 相似文献
15.
High-quality LaCuO2, elaborated by solid-state reaction in sealed tube, crystallizes in the delafossite structure. The thermal analysis under reducing atmosphere (H2/N2: 1/9) revealed a stoichiometric composition LaCuO2.00. The oxide is a direct band-gap semiconductor with a forbidden band of 2.77 eV. The magnetic susceptibility follows a Curie-Weiss law from which a Cu2+ concentration of 1% has been determined. The oxygen insertion in the layered crystal lattice induces p-type conductivity. The electrical conduction occurs predominantly by small polaron hopping between mixed valences Cu+/2+ with an activation energy of 0.28 eV and a hole mobility (μ300 K=3.5×10−7 cm2 V−1 s−1), thermally activated. Most holes are trapped in surface-polaron states upon gap excitation. The photoelectrochemical study, reported for the first time, confirms the p-type conduction. The flat band potential (Vfb=0.15 VSCE) and the hole density (NA=5.8×1017 cm−3) were determined, respectively, by extrapolating the curve C−2 versus the potential to their intersection with C−2=0 and from the slope of the linear part in the Mott-Schottky plot. The valence band is made up of Cu-3d orbital, positioned at 4.9 eV below vacuum. An energy band diagram has been established predicting the possibility of the oxide to be used as hydrogen photocathode. 相似文献
16.
Abhay Kumar Singh 《Physica B: Condensed Matter》2009,404(20):3470-3474
In this work, we report the optical properties of bulk Se93−XZn2Te5InX (X=0, 2, 4, 6 and 10) chalcogenide glasses. Refractive index, extinction coefficient, real dielectric constant (ε′), imaginary dielectric constant (ε″), absorption coefficient (α) and energy band gap were obtained from analysis of common range (250-1100 nm) UV/Visible transmittance spectrum. Besides, transmission percentages were obtained from FTIR spectra in wave number range 4000-400 cm−1.The concentration dependence structural phenomena have been explained with help of average coordination 〈z〉. 相似文献
17.
Effects of WO3 and CdO on the spectroscopic properties of Nd3+ doped tellurite glasses were investigated. The optical band gaps and Urbach energies of the samples were determined using the dependence of the absorption coefficient on the photon energy. The Urbach energies were found to vary from 0.18 to 0.25 eV as the WO3 content in the binary glasses decreased from 20.0 to 10.0 mol% while the optical band gap of the same glasses did not show an appreciable dependence on the glass composition. Judd-Ofelt (Ωt) parameters were calculated from the optical absorption spectra measured at room temperature. In all the glasses the J-O parameters follow the same trend as Ω2>Ω6>Ω4. The J-O intensity parameters were used to compute the radiative properties such as the radiative transition probabilities (Aed), branching ratios (β) and radiative lifetimes (τr) for all the possible fluorescence bands. The fluorescence spectra obtained upon 805.2 nm excitation exhibited an intense emission band centered at 1064 nm (4F3/2→4I11/2) and two weak bands at 910 nm (4F3/2→4I9/2), and 1340 nm (4F3/2→4I13/2). The stimulated emission cross-section for the 1064 nm emission was determined using the emission spectra. The highest gain bandwidth (σe×ΔλP) was determined to be 155.4 for the 0.79TeO2-0.15WO3-0.05CdO ternary glass composition, which could be more useful as promising material for the design and development of fiber amplifiers and lasers. 相似文献
18.
O.N. Ulenikov G.A. Onopenko T.V. Krapivina O.V. Gromova 《Journal of Molecular Spectroscopy》2005,230(1):78-86
A high-resolution Fourier transform spectrum of the D2MSe species (M = 82, 80, 78, 77, and 76) in the region 2300-2500 cm−1 was recorded for the first time and assigned. On the basis of these experimental data, rotation-vibration energies of the (1 1 0) and (0 1 1) vibrational states were fitted, and band centers, and rotational, centrifugal distortion, and resonance interaction parameters were determined for the main D280Se species. The obtained set of 32 fitted parameters reproduces the 647 rotation-vibration energies with a rms deviation of 0.00024 cm−1. The ν1 + ν2 and ν2 + ν3 bands of the other four isotopic species are analyzed as well. 相似文献
19.
Iouli E. Gordon Alireza Shayesteh Peter F. Bernath 《Journal of Molecular Spectroscopy》2005,229(1):145-149
Fourier transform infrared emission spectra of MnH and MnD were observed in the ground X7Σ+ electronic state. The vibration-rotation bands from v = 1 → 0 to v = 3 → 2 for MnH and from v = 1 → 0 to v = 4 → 3 for MnD were recorded at an instrumental resolution of 0.0085 cm−1. Spectroscopic constants were determined for each vibrational level and equilibrium constants were found from a Dunham-type fit. The equilibrium vibrational constant (ωe) for MnH was found to be 1546.84518(65) cm−1, the equilibrium rotational constant (Be) is 5.6856789(103) cm−1 and the eqilibrium bond distance (re) was determined to be 1.7308601(47) Å. 相似文献
20.
Hui Zhang Mei-Bo Tang Zhen-Yong Man Hao-Hong Chen Xin-Xin Yang 《Journal of Physics and Chemistry of Solids》2009,70(2):312-1257
Structural, magnetic, heat capacity, electrical and thermal transport properties are reported on polycrystalline Ba8Ni6Ge40. Ba8Ni6Ge40 crystallizes in a cubic type I clathrate structure with unit cell a=10.5179 (4) Å. It is diamagnetic with susceptibility χdia=−1.71×10-6 emu/g Oe. An Einstein temperature 75 K and a Debye temperature 307 K are estimated from heat capacity data. It exhibits n-type conducting behavior below 300 K. It shows high Seebeck coefficients (−111×10-6 V/K), low thermal conductivity (2.25 W/K m), and low electrical resistivity (8.8 mΩ cm) at 300 K. 相似文献