共查询到20条相似文献,搜索用时 31 毫秒
1.
A. M. Pashaev B. G. Tagiev O. B. Tagiev Kh. B. Ganbarova 《Journal of Applied Spectroscopy》2011,78(2):266-271
We have ground bulk samples to obtain nanoparticles of (Ga2S3)1–x
(Eu2O3)
x
solid solutions, the sizes of which were determined using an atomic force microscope. The photoluminescence spectra of the
nanoparticles were studied in the temperature interval 77–300 K. We have established the mechanisms for emission and transfer
of energy from the matrix to the rare-earth ion, and we determined the Stokes shift (ΔS = 0.7 eV), the Huang–Rhys parameter
(S = 16), and the optical phonon energy (ħ−ω = 23 meV). 相似文献
2.
We have studied photoluminescence and thermoluminescence (PL and TL) in CaGa2Se4:Eu crystals in the temperature range 77–400 K. We have established that broadband photoluminescence with maximum at 571 nm
is due to intracenter transitions 4f6 5d–4f7 (8S7/2) of the Eu2+ ions. From the temperature dependence of the intensity (log I–103/T), we determined the activation energy (E
a = 0.04 eV) for thermal quenching of photoluminescence. From the thermoluminescence spectra, we determined the trap depths:
0.31, 0.44, 0.53, 0.59 eV. The lifetime of the excited state 4f6 5d of the Eu2+ ions in the CaGa2Se4 crystal found from the luminescence decay kinetics is 3.8 μsec.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 112–116, January–February, 2009. 相似文献
3.
SiO2-TiO2 films [Si:Ti = 1:(0.06–2.3)] are obtained by the sol-gel method. The structural and photoluminescent properties of the films
and powders heat-treated at different temperatures are studied. It is shown that after 700°C the composite consists of TiO2 crystallites that are structurally similar to anatase and distributed in an amorphous SiO2 matrix. The photoluminescence spectra have maxima at 450–500 nm. The photoluminescence intensity depends on the treatment
temperature and TiO2 content.
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Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 357–361, May–June, 2007. 相似文献
4.
S. S. Novosad I. M. Matviishin I. S. Novosad O. S. Novosad 《Journal of Applied Spectroscopy》2008,75(6):826-831
We have studied the effect of lead dopant on the optical absorption, photoluminescence, and x-ray luminescence spectra, and
the scintillation characteristics of CdI2 at room temperature. The crystals for the study were grown by the Stockbarger-Bridgman method. Activation of CdI2 from the melt by the compound PbI2 leads to the appearance in the absorption spectra in the near-edge region of an activator band at 395–405 nm, which is interpreted
as an A band connected with electronic transitions from the 1S0 state to the 3P1 levels in the Pb2+ ion. For x-ray excitation, CdI2:Pb2+ crystals with optimal dopant concentration (∼1.0 mol%) are characterized by a light yield with maximum in the 570–580 nm
region that is an order of magnitude higher than for CdI2 crystals in the 490–500 nm band. For α excitation, the radioluminescence kinetics for cadmium iodide is characterized by
a very short (∼0.3 nsec) rise time and fast decay of luminescence, with τ1 ≈ 4 nsec and τ2 = 10–76 nsec. Depending on the conditions under which the crystals were obtained, the fast component fraction is 95%–99%.
The crystal is characterized by a similar scintillation pulse in the case of excitation by x-ray pulses. The radioluminescence
pulse shape for CdI2:Pb in the decay stage is predominantly exponential, with luminescence decay time constants τ1 ≈ 10 nsec and τ2 = 200–250 nsec. This system is characterized by low afterglow, at the level for the Bi4G3O12 scintillator. We have demonstrated the feasibility of using CdI2:Pb as a scintillator for detecting α particles.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 825–830, November–December, 2008. 相似文献
5.
G. A. Komandin A. S. Prokhorov V. I. Torgashev E. S. Zhukova B. P. Gorshunov A. A. Bush 《Physics of the Solid State》2011,53(4):736-744
The spectra of complex permittivity of a Ba2Mg2Fe12O22 single crystal belonging to the family of Y-type hexaferrites have been measured over a wide temperature range (10–300 K) with the aim of determining the dynamic parameters
of the phonon and magnetic subsystems in the terahertz and infrared frequency ranges (3–4500 cm−1). A factor-group analysis of the vibrational modes has been performed, and the results obtained have been compared with the
experimentally observed resonances. The oscillator parameters of all nineteen phonon modes of E
u
symmetry, which are allowed by the symmetry of the Ba2Mg2Fe12O22 crystal lattice, have been calculated. It has been found that, at temperatures below 195 and 50 K, the spectral response
exhibits new absorption lines due to magnetic excitations. 相似文献
6.
I. M. Bolesta V. V. Vistovskii N. V. Gloskovskaya M. R. Panasyuk L. I. Yaritskaya 《Physics of the Solid State》2011,53(4):799-803
It has been shown using atomic-force microscopy that the PbI2 impurity is embedded in the CdI2 crystal lattice in the form of nanocrystalline inclusions. The model of a high-energy cation exciton related to the 3
P
2 state of a free Pb2+ ion has been considered for the impurity absorption (excitation) band at 3.23 eV. The resonance narrow photoluminescence
bands with the split absorption band at 3.12 and 3.20 eV have been compared with the emission of a free Frenkel exciton. It
has been demonstrated that, in the temperature range 25–45 K, there arises a self-trapped exciton state, and the main role
in its formation is played by the bending vibrations of the CdI2 crystal lattice. The potential barrier separating the self-trapped state from the free exciton is 23 meV. The photoluminescence
band at 2.4 eV is assigned to the emission of the self-trapped high-energy cation exciton of PbI2 in the CdI2 crystal lattice. 相似文献
7.
Yu. M. Korchak M. V. Partyka V. B. Kapustyanyk S. A. Sveleba B. S. Fedor 《Journal of Applied Spectroscopy》2008,75(5):723-729
We have studied the signs of phase transitions and spatial modulation of the structure in the absorption spectra of an (NCH3)4)2Zn0.8Ni0.2Cl4 crystal. We have observed the existence of phase transitions in the given solid solution at temperatures of 155 K, 168 K,
275 K, 280 K, and 296 K. We have established that the thermooptic memory effect observed in the absorption spectra is completely
consistent with a model of defect ordering in the sample in the field of the modulated structure. According to this model,
stabilization of the sample in an incommensurable phase leads to fixing of a certain symmetry in the crystal (usually a lower
symmetry than the average symmetry of the incommensurable phase) and a metal-halogen complex corresponding to the defect wave.
As a result, we observe an appreciable shift of the intra-ionic absorption bands and an increase in their intensity.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 717–723, September–October, 2008. 相似文献
8.
A. V. Malakhovskii E. V. Eremin D. A. Velikanov A. V. Kartashev A. D. Vasil’ev I. A. Gudim 《Physics of the Solid State》2011,53(10):2032-2037
The magnetic properties of the Nd0.5Gd0.5Fe3(BO3)4 single crystal have been studied in principal crystallographic directions in magnetic fields to 90 kG in the temperature
range 2–300 K; in addition, the heat capacity has been measured in the range 2–300 K. It has been found that, below the Néel
temperature T
N = 32 K down to 2 K, the single crystal exhibits an easy-plane antiferromagnetic structure. A hysteresis has been detected
during magnetization of the crystal in the easy plane in fields of 1.0–3.5 kG, and a singularity has been found in the temperature
dependence of the magnetic susceptibility in the easy plane at a temperature of 11 K in fields B < 1 kG. It has been shown that the singularity is due to appearance of the hysteresis. The origin of the magnetic properties
of the crystal near the hysteresis has been discussed. 相似文献
9.
We have studied the effect of doping with Eu2+ and Ce3+ ions on the photoluminescence (PL) of BaGa2Se4 crystals in the temperature range 77–300 K. We have established that the broad bands with maxima at wavelengths 456 nm and
506 nm observed in the photoluminescence spectra of BaGa2Se4:Ce3+ crystals are due to intracenter transitions 5d → 2F7/2 and 5d →2F5/2 of the Ce3+ ions, while the broad photoluminescence band with maximum at 521 nm in the spectrum of BaGa2Se4:Eu2+ is associated with 4f6 5d → 4f7 (8S7/2) transitions of the Eu2+ ion. We show that in BaGa2Se4:Eu2+,Ce3+ crystals, excitation energy is transferred from the Ce3+ ions to the Eu2+ ions. 相似文献
10.
The Ac electrical conductivity and the dielectric relaxation properties of the [(C3H7)4N]2Cd2Cl6 polycrystalline sample have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies
and temperatures, 209 Hz–5 MHz and 361–418 K, respectively. The purpose is to make a difference between the electrical and
dielectric properties of the polycrystalline sample and single crystal. Besides, a detailed analysis of the impedance spectrum
suggests that the electrical properties of the material are strongly temperature-dependent. Plots of (Z" versus Z') are well
fitted to an equivalent circuit model consisting of a series combination of grains and grains boundary elements. Moreover,
the temperature dependence of the electrical conductivity in the different phases follows the Arrhenius law and the frequency
dependence of σ (ω) follows the Jonscher’s universal dynamic law. Furthermore, the modulus plots can be characterized by full
width at half height or in terms of a nonexperiential decay function φ(t) = exp(t/t)β. Finally, the imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. 相似文献
11.
A series of solid solutions with a general formula of Ca2(1-x)Sr2xAl2SiO7:Eu2+ were synthesized by a high temperature solid state reaction. The structure, diffuse reflection spectra, photoluminescence
spectra, color-coordinate parameters and lifetimes of phosphors were investigated. XRD results show that Ca2Al2SiO7 is totally miscible with Sr2Al2SiO7. These solid solution phosphors show a broad excitation band of 350–450 nm that matches well with the output lights of near-UV
LEDs and tunable emission from bluish green to yellowish green. These optical properties originate from the 4f7–4f65d transition of Eu2+ ions. The crystal field strength was considered to be tailed by controlling the host composition, which leads to the shift
of absorption band and emission band, and the varying of color coordinates.
PACS 78.55.-m; 42.70.-a; 61.05.C- 相似文献
12.
The manifestations of phase transitions and the spatial modulation of the structure of the (N(CH3)4)2CuCl4 crystal in its absorption spectra have been investigated. It has been established that the thermooptical-memory effect manifesting
itself in the absorption spectra of this crystal entirely corresponds to the model of ordering of defects and impurities in
a sample with a modulated structure. It is shown that, as a result of stabilization of the crystal studied in the incommensurate
phase, its symmetry and the symmetry of the metal-halogen complex in it lower depending on the defect wave. This manifests
itself as a marked shift of the intraionic-absorption bands and an increase in their intensity.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 386–390, May–June, 2005. 相似文献
13.
F. Guo J. Ru H. Li N. Zhuang B. Zhao J. Chen 《Applied physics. B, Lasers and optics》2009,94(3):437-441
Lithium terbium molybdate (LiTb(MoO4)2) single crystal was grown by the Czochralski method. The lattice parameters of the crystal were determined by X-ray diffraction
analysis. The absorption coefficient and the Faraday rotation spectrum (B=1.07 T) were investigated at wavelengths of 400–1500 nm at room temperature. Verdet constants of LiTb(MoO4)2 crystal at 532-, 633- and 1064-nm wavelengths were measured by the extinction method. The results show that LiTb(MoO4)2 crystal has a larger magneto-optical figure of merit than that of terbium gallium garnet at wavelengths of 600–1500 nm. 相似文献
14.
L. Kovács M. Mazzera E. Beregi R. Capelletti 《Applied physics. B, Lasers and optics》2009,94(2):273-277
Several weak absorption bands have been observed in the optical absorption spectra of pure and rare-earth-doped YAl3(BO3)4 single crystals in the 3350– 3650 cm−1 wave number region. Two of them, peaking at about 3377 cm−1 and 3580 cm−1 in the 8 K spectra, appear in most of the samples. They are tentatively attributed to the stretching mode of OH− ions incorporated in the crystal during the growth. An additional absorption band at about 5250 cm−1 at 8 K has also been detected in almost all samples. The temperature and polarization dependences of these bands, and their
possible origin, are discussed. 相似文献
15.
M. D. Volnyanskii S. N. Plyaka M. P. Trubitsyn Yahia A. H. Obaidat 《Physics of the Solid State》2012,54(3):499-503
The electrical properties of a lithium heptagermanate (Li2Ge7O15) crystal have been studied in DC and AC measuring fields at temperatures from 500 to 700 K. In a DC field, a substantial
decrease of electrical conductivity σ with time has been detected. On the basis of kinetic dependences σ(t), estimates of the charge carrier diffusion coefficient D have been obtained. In the frequency range 101–105 Hz, the spectra of complex impedance ρ*(f) have been measured. The analysis of diagrams in the complex plane (ρ″–ρ′) has been performed within the equivalent circuit
approach. It has been shown that, in the considered temperature and frequency intervals, the electrical properties of Li2Ge7O15 crystals have been determined by the hopping conduction of interstitial lithium ions A
Li and accumulation of charge carriers near the blocking Pt electrodes. 相似文献
16.
L. N. Korotkov T. N. Korotkova R. R. Levitskii S. I. Sorokov A. S. Vdovych 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1331-1334
The time dependences of polarization of K0.88(NH4)0.12H2PO4 mixed crystal have been studied within the temperature range of 74–100 K. Two mechanisms of polarization relaxation were
found. The first mechanism is caused by domain walls lateral motion and their interaction with point lattice defects. The
second one supposedly is due to polar regions infiltration through the regions of frustrated paraelectric phase. 相似文献
17.
A. N. Romanov D. N. Vtyurina E. V. Haula D. P. Shashkin N. A. Pimkin M. S. Kuznetsov I. S. Lisitsky V. N. Korchak 《Russian Journal of Physical Chemistry B, Focus on Physics》2016,10(5):735-739
Single-crystal samples of RbY2Cl7 ternary chloride containing an Bi+ isomorphic impurity are prepared for the first time. The optical absorption spectra in the visible region and photoluminescence spectra in the near-IR associated with the presence of Bi+ impurity center are studied. The kinetics of the photoluminescence decay is investigated. The influence of the symmetry of the crystal field on the arrangement of the energy levels and on the characteristics of the absorption and photoluminescence spectra of Bi+ is demonstrated. 相似文献
18.
S. I. Vorob’ev E. I. Golovenchits V. P. Koptev E. N. Komarov S. A. Kotov V. A. Sanina G. V. Shcherbakov 《JETP Letters》2010,91(10):512-517
The magnetic properties of the EuMn2O5 multiferroic (samples consisting of single crystals and ceramic samples) have been investigated by the muon-spin-relaxation
(μSR) method in the temperature range of 10–300 K. Below the magnetic ordering temperature T
N = 40 K, the loss of the polarization of muons and the effect of the external magnetic field have been observed. Both phenomena
can be explained by an additional channel of the depolarization of muons owing to the appearance of muons in a medium with
a low electron density due to the charge separation process (the redistribution of the electron density in the phase transition
process). The “memory” phenomenon has been revealed in a sample in the external magnetic field; the memory relaxation time
depends on the size of the structure units of the samples (single crystals or ceramic grains). 相似文献
19.
P. A. Popov N. V. Moiseev V. N. Shlegel’ N. V. Ivannikova 《Physics of the Solid State》2010,52(9):1855-1858
The thermal conductivity and the heat capacity of a single crystal of bismuth orthogermanate Bi4Ge3O12 have been experimentally investigated in the temperature ranges 50–300 and 56–300 K, respectively. The temperature dependences
of the phonon mean free path, the characteristic Debye temperature, and the changes in the entropy and enthalpy have been
calculated. 相似文献
20.
Photoexcited states of NH4BPh4 (TPhBA) particles embedded in mesoporous frameworks of different pore sizes were studied by combined electron paramagnetic
resonance (EPR), optical and photoluminescence techniques. A distribution of triplet states with short and long electron–hole
distances was found. While EPR studies on TPhBA bulk sample suggested that the formation of electron–hole pairs upon the excitation
was caused by electron capture on electron traps, the samples in mesoporous frameworks exhibit two ways of the pair formation.
The first one is attributed to the capture on phenyl rings and another one is to be thought as the capture of electrons on
adsorbed oxygen molecules. These results are also consistent with the thermoluminescence spectra and EPR studies of the photoexcited
samples during annealing. 相似文献