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1.
Samples of the composition TlNiS2 in the hexagonal system with the unit cell parameters a=12.28 Å, c=19.32 Å, and ρ=6.90 g/cm3 are synthesized. The results of the investigation into the electrical and thermoelectrical properties of TlNiS2 samples in the temperature range 80–300 K indicate that TlNiS2 is a p-type semiconductor. It is found that, at temperatures ranging from 110 to 240 K, TlNiS2 samples in a dc electric field possess variable-range-hopping conduction at the states localized in the vicinity of the Fermi level. The density of localized states near the Fermi level is determined to be NF=9×1020 eV?1 cm?3, and the scatter of the states is estimated as J≈2×10?2 eV. In the temperature range 80–110 K, TlNiS2 exhibits activationless hopping conduction. At low temperatures (80–240 K), the thermopower of TlNiS2 is adequately described by the relationship α(T)=A+BT, which is characteristic of the hopping mechanism of charge transfer. In the case when the temperature increases to the temperature of the onset of intrinsic conduction with the activation energy ΔE=1.0 eV, there arise majority intrinsic charge carriers of both signs. This leads to an increase in the electrical conductivity σ and, at the same time, to a drastic decrease in the thermopower α; in this case, the thermopower is virtually independent of the temperature. 相似文献
2.
The anionic conductivity of HoF3 single crystals with a β-YF3 structure (orthorhombic crystal system, space group Pnma) is investigated over a wide range of temperatures (323–1073 K). The unit cell parameters of HoF3 crystals are as follows: a=0.6384±0.0009 nm, b=0.6844±0.0009 nm, and c=0.4356±0.0005 nm. It is revealed that the conductivity anisotropy of the HoF3 crystals is insignificant over the entire temperature range covered. The crossover from one mechanism of ion transfer to another mechanism is observed near the critical temperature Tc≈620 K. The activation enthalpy of electrical conduction is found to be ΔH1=0.744 eV at T<Tc and ΔH2=0.43 eV at T>Tc. The fluorine vacancies are the most probable charge carriers in HoF3 crystals. The fluorine ionic conductivities at temperatures of 323, 500, and 1073 K are equal to 5×10?10, 5×10?6, and 2×10?3 S cm?1, respectively. 相似文献
3.
A. A. Smirnov I. N. Ogorodnikov V. A. Pustovarov L. I. Isaenko V. Yu. Yakovlev 《Optics and Spectroscopy》2008,105(3):377-379
The efficiency of formation and time evolution of radiation-induced structural defects and pulsed luminescence in KPb2Cl5 crystals under the action of a single electron pulse (E = 250 keV, τ = 20 ns) have been investigated. The spectra (1.1–3.8 eV) and relaxation kinetics (time interval 5 × 10?8?5 s) of transient optical absorption and the pulsed cathodoluminescence spectra and decay kinetics (1.4–3.1 eV) have been measured in the temperature range 80–300 K. It is revealed that the induced optical density and its time evolution depend strongly on temperature, and the absorption relaxation time contains several components and reaches several seconds at T = 300 K. The decay kinetics of transient absorption and pulsed cathodoluminescence kinetics have different orders and are controlled by different relaxation processes. 相似文献
4.
The relaxation electronic phenomena occurring in TlGa0.99Fe0.01Se2 single crystals in an external dc electric field are investigated. It is established that these phenomena are caused by electric charges accumulated in the single crystals. The charge relaxation at different electric field strengths and temperatures, the hysteresis of the current-voltage characteristic, and the electric charge accumulated in the TlGa0.99Fe0.01Se2 single crystals are consistent with the relay-race mechanism of transfer of a charge generated at deep-lying energy levels in the band gap due to the injection of charge carriers from the electric contact into the crystal. The parameters characterizing the electronic phenomena observed in the TlGa0.99Fe0.01Se2 single crystals are determined to be as follows: the effective mobility of charge carriers transferred by deep-lying centers μf=5.6×10?2 cm2/(V s) at 300 K and the activation energy of charge transfer ΔE=0.54 eV, the contact capacitance of the sample C c =5×10?8 F, the localization length of charge carriers in the crystal d c =1.17×10?6 cm, the electric charge time constant of the contact τ=15 s, the time a charge carrier takes to travel through the sample t t =1.8×10?3 s, and the activation energy of traps responsible for charge relaxation ΔE σ = ΔE Q = 0.58 eV. 相似文献
5.
M. D. Volnyanskii A. Yu. Kudzin S. N. Plyaka Z. Balasme 《Physics of the Solid State》2004,46(11):2012-2014
Dc and ac electrical conductivity of lead molybdate crystals is studied in the temperature range 300–550 K. The electrical conductivity was shown to have electronic (hole) impurity character. The I–V characteristics are typical of a space charge-limited current. The carrier mobility was estimated to be 10?5 cm2 V?1 sat T=300 K. The results of the study suggest the hopping mechanism of conduction in PbMoO4 crystals. 相似文献
6.
V. V. Bakovets I. V. Yushina O. V. Antonova T. A. Pomelova 《Optics and Spectroscopy》2016,121(6):862-866
Submicron samples of Y2O3:Eu3+ phosphor with elevated photoluminescence (PL) efficiency and activator concentration of 9 at % obtained by the sol–gel method were investigated by diffuse reflection spectroscopy and PL spectroscopy. It is found that the diffuse reflection spectrum in the vicinity of the fundamental absorption edge (<300 nm) is distorted by the superposition of the PL of Eu3+ ions, as a result of which the calculated value of optical band gap E g of the Y2O3 matrix is overestimated. An algorithm for eliminating the PL influence on the absorption edge is proposed, and the correct E g values are found to be 4.61 ± 0.12 and 4.50 ± 0.12 eV for annealing at 700 and 1300°C, respectively. 相似文献
7.
A. M. Kalashnikova V. V. Pavlov R. V. Pisarev L. N. Bezmaternykh M. Bayer Th. Rasing 《JETP Letters》2004,80(5):293-297
The optical spectra and the second-harmonic generation (SHG) are studied in a noncentrosymmetric GdFe3(BO3)4 magnet. In the region of weak absorption (α~20–400 cm?1) below ~3 eV, three absorption bands are distinguished, which can be unambiguously assigned to forbidden electronic transitions from the ground 6A1 state of the Fe3+ ion to its excited states 4T1(~1.4 eV), 4T2(~2 eV), and 4A1, 4E(~2.8 eV). Intense absorption begins in the region above 3 eV (α~2–4×105 cm?1), where two bands at ~4.0 and 4.8 eV are observed, which are caused by allowed electric dipole charge-transfer transitions. The spectral features of SHG in the 1.2–3.0-eV region are explained by a change in the SHG efficiency caused by a change in the phase mismatch. It is shown that in the weak absorption region, phase matching can be achieved for SHG. 相似文献
8.
Layered single crystals of the TlGa0.5Fe0.5Se2 alloy in a dc electric field at temperatures ranging from 128 to 178 K are found to possess variable-range-hopping conduction along natural crystal layers through states localized in the vicinity of the Fermi level. The parameters characterizing the electrical conduction in the TlGa0.5Fe0.5Se2 crystals are estimated as follows: the density of states near the Fermi level NF = 2.8 × 1017 eV?1 cm?3, the spread in energy of these states ΔE = 0.13 eV, the average hopping length Rav = 233 Å, and the concentration of deep-lying traps N t = 3.6 × 1016 cm?3. 相似文献
9.
V. S. Bilanych N. D. Baisa V. M. Rizak I. M. Rizak V. M. Holovey 《Physics of the Solid State》2003,45(1):82-86
This paper reports on the results of measurements of the internal friction Q?1 and the shear modulus G of Li2B4O7 single crystals along the crystallographic directions [100] and [001] in the temperature range 300–550 K for strain amplitudes of (2–10)×10?5 at infralow frequencies. The anomalies observed in Q?1 and G in the temperature range 390–410 K are due to thermal activation of the mobility of lithium cations and their migration from one energetically equivalent position to another. A jump in the internal friction background is revealed in the vicinity of the Q?1 and G anomalies for the Li2B4O7 crystal. The magnitude of this jump depends on the crystallographic direction. 相似文献
10.
L. K. Aminov S. I. Nikitin N. I. Silkin R. V. Yusupov 《Physics of the Solid State》2002,44(8):1558-1563
The luminescence spectra of a KZnF3: Tl+ crystal are investigated in the energy range from 4.75 to 5.9 eV at temperatures of 10–300 K upon excitation into the A absorption band (5.7–6.3 eV). At T=300 K, the luminescence spectra exhibit an intense band with a maximum at 5.45 eV, which is attributed to single Tl+ ions substituted for K+ ions. The 5.723-eV intense narrow band observed at T<20 K is assigned to the 3Γ1u-1Γ1g zero-phonon transition, which is weakly allowed by the hyperfine interaction. The luminescence decay is studied as a function of temperature. The main characteristics of the luminescence spectra are adequately described in terms of the semiclassical theory based on the Franck-Condon principle and the Jahn-Teller effect for an excited sp configuration of the Tl+ ion with the use of the parameters obtained earlier from analyzing the absorption spectra of the system under investigation. 相似文献
11.
The lithium dihydrogen phosphate LiH2PO4 has been investigated by X-ray powder diffraction, scanning electron microscopy (SEM), and electrical impedance spectroscopy. The Rietveld refinements based on the XRD patterns show that the compound is crystallized in the orthorhombic system with Pna21 space group, and the refined unit cell parameters are a = 6.2428 Å, b = 7.6445 Å, and c = 6.873 Å. The electrical properties were studied using complex impedance spectroscopy as a function of frequency (104–107 Hz) at various temperatures (300–400 K). The Nyquist plots are well fitted to an equivalent circuit consisting of a series of combination of grains and inhomogeneous electrode surface effect. The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. Moreover, the near value of the activation energies obtained from the equivalent circuit and analysis of M″ confirms that the transport is through ion hopping mechanism dominated by the motion of the proton in the structure of the investigated material. 相似文献
12.
The structural, mechanical, electronic and thermoelectric properties of the low temperature orthorhombic perovskite phase of CH3NH3PbI3 have been investigated using density functional theory (DFT). Elastic parameters bulk modulus B, Young’s modulus E, shear modulus G, Poisson’s ratio ν and anisotropy value A have been calculated by the Voigt–Reuss–Hill averaging scheme. Phonon dispersions of the structure were investigated using a finite displacement method. The relaxed system is dynamically stable, and the equilibrium elastic constants satisfy all the mechanical stability criteria for orthorhombic crystals, showing stability against the influence of external forces. The lattice thermal conductivity was calculated within the single-mode relaxation-time approximation of the Boltzmann equation from first-principles anharmonic lattice dynamics calculations. Our results show that lattice thermal conductivity is anisotropic, and the corresponding lattice thermal conductivity at 150 K was found to be 0.189, 0.138, and 0.530 Wm?1K?1 in the a, b, and c directions. Electronic structure calculations demonstrate that this compound has a DFT direct band gap at the gamma point of about 1.57 eV. The electronic transport properties have been calculated by solving the semiclassical Boltzmann transport equation on top of DFT calculations, within the constant relaxation time approximation. The Seebeck coefficient S is almost constant from 50 to 150 K. At temperatures 100 and 150 K, the maximal figure of merit is found to be 0.06 and 0.122 in the direction of the c-axis, respectively. 相似文献
13.
M. G. Gornov M. N. Ber Yu. B. Gurov S. V. Lapushkin P. V. Morokhov V. A. Pechkurov N. O. Poroshin V. G. Sandukovsky M. V. Tel’kushev B. A. Chernyshev 《JETP Letters》2003,77(7):344-348
The formation of the 5H superheavy hydrogen isotope was experimentally sought in the reactions induced by stopped π? mesons absorbed by 9Be nuclei. Peaks in missing-mass spectra were observed in two reaction channels, 9Be(π?, pt)X and 9Be(π?, dd)X, and were attributed to the 5H resonance states. The lowest state has parameters Er=5.5±0.2 MeV and Г=5.4±0.5 MeV [Er is the resonance energy measured from the (triton + two neutrons) threshold]. Therefore, 5H is bound more weakly than 4H. Excited states of 5H were also observed. All three resonance levels (E1r=10.6±0.3 MeV, Г1r=6.8±0.5 MeV; E2r=18.5±0.4 MeV, Г2r=4.8±1.3 MeV; E3r=26.7±0.4 MeV, Г3r=3.6±1.3 MeV) can decay into five free nucleons. 相似文献
14.
I. G. Orletskii P. D. Mar’yanchuk M. N. Solovan V. V. Brus E. V. Maistruk D. P. Kozyarskii S. L. Abashin 《Physics of the Solid State》2016,58(5):1058-1064
Thin films Cu2ZnSnS4 (up to 0.9 μm thick) with p-type conductivity and band gap Eg = 1.54 eV have been prepared by the spray pyrolysis of 0.1 M aqueous solutions of the salts CuCl2 · 2H2O, ZnCl2 · 2H2O, SnCl4 · 5H2O, and (NH2)2CS at a temperature TS = 290°C. The electrophysical properties of the films have been analyzed using the model for polycrystalline materials with electrically active grain boundaries. The energy and geometric parameters of the grain boundaries have been determined as follows: the height of the barriers is Eb ≈ 0.045–0.048 eV, and the thickness of the depletion region is δ ≈ 3.25 nm. The effective concentrations of charge carriers p0 = 3.16 × 1018 cm–3 and their mobilities in crystallites μp = 85 cm2/(V s) have been found using the technique for determining the kinetic parameters from the absorption spectra of thin films at a photon energy hν ≈ Eg. The density of states at grain boundaries Nt = 9.57 × 1011 cm–2 has been estimated. 相似文献
15.
New niobium beryllide Nb3Be with A15 structure and lattice parameter a=0.5187±0.0007 nm, coexisting (3–5%) with a tetragonal phase, presumably, of an ordered solid solution with parameters a=0.5414±0.0008 nm and c=0.6378±0.0009 nm, was synthesized by thermal treatment (875–110°C) of amorphous film coatings containing 26.8–32.4 at. % Be and formed from short-period Nb and Be layers by magnetron sputtering. The domain of existence of the Nb3Be phase and the critical superconducting transition temperature (10.0 K and a transition width of 2.5 K) were determined and the X-ray structural data for structure identification were obtained. 相似文献
16.
N. I. Kadyrova Yu. G. Zaynulin A. P. Tyutyunnik N. V. Melnikova I. S. Ustinova A. V. Korolev 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1163-1165
Tm x Cu3V4O12, a perovskite-like oxide (space group, Im-3; Z = 2; a = 7.279–7.293 Å) containing vacancies in its cationic sublattice, was obtained barothermally (P = 7.0–9.0 GPa, t = 1000–1100°C) for the first time. The temperature dependences on the electrical resistivity (10–300 K) and the magnetic susceptibility (0–300 K) were investigated. It was shown that the oxide Tm x Cu3V4O12 is characterized by metal-type conductivity and paramagnetic properties. 相似文献
17.
A. I. Abramovich O. Yu. Gorbenko A. R. Kaul L. I. Koroleva A. V. Michurin 《Physics of the Solid State》2004,46(9):1711-1716
Magnetic, elastic, magnetoelastic, transport, and magnetotransport properties of the Eu0.55Sr0.45MnO3 ceramics have been studied. A break was detected in the temperature dependence of electrical resistivity ρ(T) near the temperature of the magnetic phase transformation (41 K), with the material remaining an insulator down to the lowest measurement temperature reached (ρ=106 Ω cm at 4.2 K). In the interval 4.2≤T≤50 K, the isotherms of the magnetization, volume magnetostriction, and ρ were observed to undergo jumps at the critical field HC1, which decreases with increasing T. For 50≤T≤120 K, the jumps in the above curves persist, but the pattern of the curves changes and HC1 grows with increasing T. The magnetoresistance Δρ/ρ = (ρ H ?ρH=0)/ρ H is positive for H<HC1 and passes through a maximum at 41 K, where Δρ/ρ = 6%. For H>HC1, the magnetoresistance is negative, passes through a minimum near 41 K, and reaches a colossal value of 3×105 % at H=45 kOe. The volume magnetostriction is negative and attains a giant value of 4.5×10?4atH=45 kOe. The observed properties are assigned to the existence of three phases in Eu0.55Sr0.45MnO3, namely, a ferromagnetic (FM) phase, in which carriers are concentrated because of the gain in s-d exchange energy, and two antiferromagnetic (AFM) phases of the A and CE types. Their fractional volumes at low temperatures were estimated to be as follows: ~3% of the sample volume is occupied by the FM phase; ~67%, by the CE-type AFM phase; and ~30%, by the A-type AFM phase. 相似文献
18.
A. P. Martynenko 《Physics of Atomic Nuclei》2008,71(1):125-135
Corrections of order α
5 and α
6 are calculated for muonic hydrogen in the fine-structure interval ΔE
fs = E(2P
3/2) − E(2P
1/2) and in the hyperfine structure of the 2P
1/2-and 2P
3/2-wave energy levels. The resulting values of ΔE
fs = 8352.08 μeV, ΔẼ
hfs(2P
1/2) = 7819.80 μeV, and ΔẼ
hfs(2P
3/2) = 3248.03 μeV provide reliable guidelines in performing a comparison with relevant experimental data and in more precisely
extracting the experimental value of the (2P–2S) Lamb shift in the muonic-hydrogen atom.
Original Russian Text ? A.P. Martynenko, 2008, published in Yadernaya Fizika, 2008, Vol. 71, No. 1, pp. 126–136. 相似文献
19.
High-frequency broad-band (65–240 GHz) EPR is used to study impurity centers of bivalent chromium in a CdGa2S4 crystal. It is found that the EPR spectra correspond to tetragonal symmetry. The spin Hamiltonian H = βB · g · S + B 2 0 O 2 0 + B 4 0 O 4 0 + B 4 4 O 4 4 with the parameters B 2 0 =23659±2 MHz, B 4 0 =1.9±1 MHz, |B 4 4 |=54.2±2 MHz, g‖=1.93±0.02, and g⊥=1.99±0.02 is used to describe the observed spectra. It is concluded that chromium ions occupy one of the tetrahedrally coordinated cation positions. 相似文献
20.
Lead-free Na0.5Bi0.5TiO3 (NBT) and (1 ? x)Na0.5Bi0.5TiO3 + xBaTiO3 with x = 0.1 and 0.2 (where x = 0.1 and 0.2 are named as NBT1 and NBT2, respectively), (1 ? y)Na0.5Bi0.5TiO3 + yBa0.925Nd0.05TiO3 with y = 0.1 and 0.2 (where y = 0.1 and 0.2 are named as NBT3 and NBT4, respectively)-based relaxor ferroelectric ceramics were prepared using the sol-gel method. The crystal structure was investigated by X-ray diffraction (XRD) at room temperature (RT). The XRD patterns confirmed the presence of the rhombohedral phase in all the samples. The electrical properties of the present NBT-based samples were investigated by complex impedance and the modulus spectroscopy technique in the temperature range of RT–600 °C. The AC conductivity was found to increase with the substitution of Ba2+ ions to the NBT sample whereas it significantly decreased with the addition of Nd3+ ions. The more anion vacancies in Ba-added samples and the lower anion vacancies in Nd-added samples were found to be responsible for higher and lower conductivities, respectively. 相似文献