共查询到20条相似文献,搜索用时 29 毫秒
1.
T. I. Milenov V. I. Dimov P. M. Rafailov M. M. Gospodinov 《Applied Physics A: Materials Science & Processing》2008,92(3):643-649
Lattice defects in a scintillation detector made of Bi4Ge3O12 (BGO) could severely impact detector efficiency via non-radiative transfer of electron excitation, thus making thorough investigations
of these defects highly important. Here we present a combined experimental and theoretical study of two- and three-dimensional
defects in a Czochralski-grown BGO crystal. Upon examination by transmission electron microscopy the selected-area electron
diffraction (SAED) patterns in two neighboring parts of the specimen reveal different kinds of two- and three-dimensional
defects. Three sub-grains misoriented at 2.47° with reference to each other and probable presence of stacking faults lying
in {011} planes were observed in the first examined local area. The SAED image taken from an area in the close neighborhood
is much more complicated and is explained in terms of the superposition of reflections from: (i) a partially textured GeO2 second-phase inclusion; (ii) the basic lattice of BGO and (iii) a superlattice-like structure based on the BGO lattice. The
atomic structure of such a superlattice-like structure was theoretically modeled and the corresponding simulated SAED patterns
were found to be in good agreement with the experimentally observed one. 相似文献
2.
Wenwei Ge Hong Liu Xiangyong Zhao Xiaobing Li Xiaoming Pan Di Lin Haiqing Xu Xiangping Jiang Haosu Luo 《Applied Physics A: Materials Science & Processing》2009,95(3):761-767
In this paper, a single crystal of 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal
possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties
were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants
for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T
m, ε
m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718),
(305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were
obtained by investigating the piezoelectric constants d
33 as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d
33 values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied
during the poling process. The as-grown 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10−11 Ω−1⋅m−1 and 3.95×10−9 Ω−1⋅m−1 at 25°C and 150°C for the 〈001〉 oriented crystal sample. 相似文献
3.
Xinbing Jiao Jingsong Wei Fuxi Gan Mufei Xiao 《Applied Physics A: Materials Science & Processing》2009,94(3):627-631
The dependence of thermal properties of Ag8In14Sb55Te23 phase-change memory materials in crystalline and amorphous states on temperature was measured and analyzed. The results show
that in the crystalline state, the thermal properties monotonically decrease with the temperature and present obvious crystalline
semiconductor characteristics. The heat capacity, thermal diffusivity, and thermal conductivity decrease from 0.35 J/g K,
1.85 mm2/s, and 4.0 W/m K at 300 K to 0.025 J/g K, 1.475 mm2/s, and 0.25 W/m K at 600 K, respectively. In the amorphous state, while the dependence of thermal properties on temperature
does not present significant changes, the materials retain the glass-like thermal characteristics. Within the temperature
range from 320 K to 440 K, the heat capacity fluctuates between 0.27 J/g K and 0.075 J/g K, the thermal diffusivity basically
maintains at 0.525 mm2/s, and the thermal conductivity decreases from 1.02 W/m K at 320 K to 0.2 W/m K at 440 K. Whether in the crystalline or amorphous
state, Ag8In14Sb55Te23 are more thermally active than Ge2Sb2Te5, that is, the Ag8In14Sb55Te23 composites bear stronger thermal conduction and diffusion than the Ge2Sb2Te5 phase-change memory materials. 相似文献
4.
M. Mazzera A. Baraldi E. Buffagni R. Capelletti E. Beregi I. Földvári N. Magnani 《Applied physics. B, Lasers and optics》2011,104(3):603-617
Yttrium aluminium borate single crystals, doped with 1 and 4 mol% of Pr3+, were analyzed in the wave number range 500–25000 cm−1 and temperature range 9–300 K by means of high-resolution Fourier transform spectroscopy. In spite of the complex spectra,
exhibiting broad and split lines, the energy level scheme was obtained for several excited manifolds. The careful analysis
of the spectra as a function of the temperature allowed us to identify most of the sublevels of the ground manifold. The thermally
induced line shift, well described by a single-phonon coupling model, could be exploited to provide information about the
energy of the phonons involved. The orientation of the dielectric ellipsoid and of the dipole moments associated to a few
transitions was also determined from linear dichroism measurements. The experimental data were fitted in the framework of
the crystal-field theory, but the agreement was not satisfactory, as already reported for Pr3+ ion in other matrices. Additional discrepancies came from the dichroic spectra analysis and the line splitting, possibly
associated to hyperfine interaction. Some causes which might be responsible for the difficulties encountered in the Pr3+ ion theoretical modelling are discussed. 相似文献
5.
The magneto-transport properties of thick relaxed A-site deficient films
having the composition Pr
Sr0.3MnO3 (P□SMO
with the □ symbol for the Pr vacancy) and Pr0.7Sr
MnO3 (PS□MO) are studied. A
direct comparison with a Pr0.7Sr0.3MnO3 (PSMO)completely relaxed film, deposited under the same growth conditions, shows
a reduction of the in-plane parameter a100 associated to an enhancement
of the out-plane parameter. The strains (bulk strain εB
and biaxial Jahn-Teller strain εJ-T) do vary with the
nature of the cationic vacancy. For example, an enhancement of εB of 9% in the PS□MO film (Sr deficient) produces a decrease
of TC of 30 K, whereas the Pr deficient P□SMO film exhibits a
large reduction of both εB (-16%) and εJ-T (divided by a factor of 5), which enhances TC of 12 K, similarly to previous observations on bulk ceramics. With a reduced
resistivity (ρ<0.02 Ω cm), the obtained Pr-deficient film,
P□SMO, exhibits the best magneto-transport properties with a decreasing
magnetoresistance sensitivity at low field. 相似文献
6.
K.?Sudheendran M.?Ghanashyam?Krishna K.?C.?James?Raju 《Applied Physics A: Materials Science & Processing》2009,95(2):485-492
Bismuth Zinc niobate (Bi1.5Zn1.0Nb1.5O7) thin films were deposited by pulsed laser deposition (PLD) method on fused silica substrates at different oxygen pressures.
The structural, microwave dielectric and optical properties of these thin films were systematically studied for both the as-deposited
and the annealed films at 600°C. The as-deposited films were all amorphous in nature but crystallized on annealing at 600°C
in air. The surface morphology as studied by atomic force microscopy (AFM) reveals ultra-fine grains in the case of as-deposited
thin films and cluster grain morphology on annealing. The as-deposited films exhibit refractive index in the range of 2.36–2.53
(at a wavelength of 750 nm) with an optical absorption edge value of 3.30–3.52 eV and a maximum dielectric constant of 11
at 12.15 GHz. On annealing the films at 600°C they crystallize to the cubic pyrochlore structure accompanied by an increase
in band gap, refractive index and microwave dielectric constant. 相似文献
7.
S. Canulescu T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2008,93(3):771-778
The mass distributions of the species generated by laser ablation from a La0.6Ca0.4MnO3 target using laser irradiation wavelengths of 193 nm, 266 nm and 308 nm have been investigated with and without a synchronized
gas pulse of N2O. The kinetic energies of the species are measured using an electrostatic deflection energy analyzer, while the mass distributions
of the species were analyzed with a quadrupole mass filter.
In vacuum (pressure 10−7 mbar), the ablation plume consists of metal atoms and ions such as La, Ca, Mn, O, LaO, as well as multiatomic species, e.g.
LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small
amounts.
The interaction of a reactive N2O gas pulse with the ablation plume leads to an increase in plume reactivity, which is desired when thin manganite films are
grown, in order to incorporate the necessary amount of oxygen into the film. The N2O gas pulse appears to have a significant influence on the oxidation of the Mn species in the plume, and on the creation of
negative ions, such as LaO−,O− and O2−. 相似文献
8.
N. A. Kalanda G. G. Gorokh M. V. Yarmolich A. A. Lozovenko E. Yu. Kanyukov 《Physics of the Solid State》2016,58(2):351-359
A method has been developed for fabricating nanoporous matrices based on anodic aluminum oxide for the deposition of ferromagnetic nanoparticles in them. The modes of deposition of strontium ferromolybdate thin films prepared by the ion-plasma method have been worked out, and the magnetic and magnetoresistive properties, structure, and composition of the films have been investigated. It has been revealed that the microstructure and properties of the strontium ferromolybdate films deposited by ionplasma sputtering depend on the deposition rate and the temperature of the substrate. Based on the measurement of the electrical resistivity of nanoheterostructures in a magnetic field, it has been found that the magnetoresistance reaches 14% at T = 15 K and B = 8 T, which is due to the manifestation of tunneling magnetoresistance. 相似文献
9.
S. I. Vorob’ev D. S. Andrievskii S. G. Barsov A. L. Getalov E. I. Golovenchits E. N. Komarov S. A. Kotov A. Yu. Mishchenko V. A. Sanina G. V. Shcherbakov 《Journal of Experimental and Theoretical Physics》2016,123(6):1017-1024
A comparative μSR study of ceramic samples of the EuMn2O5 and Eu0.8Ce0.2Mn2O5 multiferroics is performed in the temperature range from 15 to 300 K. It is found that the Ce doping of the EuMn2O5 sample slightly reduces the temperature of the magnetic phase transition from T N = 45 K for the EuMn2O5 sample to T N = 42.5 K for the Eu0.8Ce0.2Mn2O5 sample. Below the temperature T N for both samples, there are two types of localization of a thermalized muon with different temperature dependences of the precession frequency of the magnetic moment of the muon in an internal magnetic field. The higher frequency in both samples refers to the initial antiferromagnetic matrix. The behavior of this frequency in Eu0.8Ce0.2Mn2O5 follows the Curie–Weiss law with the exponent β = 0.29 ± 0.02, which differs from the value β = 0.39 standard for 3D Heisenberg magnetics and is observed in EuMn2O5, because of the strong frustration of the doped sample. The temperature-independent low frequency is due to the presence of Mn3+–Mn4+ ferromagnetic pairs located along the b axis of the antiferromagnetic matrix and in the regions of phase separation, which contain such ion pairs and e g electrons recharging them. In both samples, polarization losses are the same (about 20%) and are associated with the formation of Mn4+–Mn4+ + Mu complexes near Mn3+–Mn4+ ferromagnetic pairs. In the temperature interval from 25 to 45 K, the separation of the Eu0.8Ce0.2Mn2O5 structure into two fractions where the relaxation rates of polarization of muons differ by an order of magnitude is revealed. This effect is due to a change in the state of regions of phase separation (1D superlattices) at the indicated temperatures. Such effect in EuMn2O5 is significantly weaker. 相似文献
10.
L. T. Denisova N. V. Belousova N. A. Galiakhmetova V. M. Denisov E. O. Golubeva 《Physics of the Solid State》2018,60(7):1303-1307
Differential scanning calorimetry has been used to study the influence of temperature on the heat capacity of synthesized vanadates Zn2V2O7, (Cu0.56Zn1.44)V2O7, and (Cu1.0Zn1.0)V2O7. It is found that dependences Cp = f(T) have extremes. The thermodynamic properties of Zn2V2O7 have been determined. 相似文献
11.
The formation of an intermediate phase in SrFe12O19/La0.9Ca0.1MnO3 composites was demonstrated for the first time using only Mössbauer spectroscopy. The SrFe12O19/La0.9Ca0.1MnO3 composite was prepared by the two-stage (sol–gel and hydrothermal) synthesis with varying initial conditions. The X-ray diffraction studies showed that the composite consisted of two phases: well-formed structures of manganite La0.9Ca0.1MnO3 and hexagonal ferrite SrFe12O19. It was found that nanocrystalline La0.9Ca0.1MnO3 particles with size d ? 150 nm formed in the composites at the surface of plate-like SrFe12O19 crystallites. The Mössbauer studies showed that the composite contained additional (intermediate) phase La0.9Ca0.1Mn(Fe)O3 that formed at the interface between SrFe12O19 and La0.9Ca0.1MnO3 phases. The intermediate phase concentration increased with the molar content of La0.9Ca0.1MnO3; in this case, the fraction of the surface of SrFe12O19 crystallites coated with La0.9Ca0.1MnO3 increased, which led to the increase in the total area of the interface surface and the intermediate phase concentration. 相似文献
12.
Organic–inorganic hybrid sample [N(C4H9)4]2Cu2Cl6 was prepared via the reaction between copper chloride and tetrabutylammonium chloride. The compound was characterized by
X-ray powder diffraction, IR, Raman, differential scanning calorimetry (DSC), DTA-TGA analysis and electrical impedance spectroscopy.
DSC studies indicate a presence of one-phase transition at 343 K. The complex impedance of compound [N(C4H9)4]2Cu2Cl6 have been investigated in temperature and frequency ranges 300–380 K and 200 Hz–5 MHz, respectively. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination
of bulk resistance R
p and constant phase elements CPE. The frequency dependence of the conductivity is interpreted in term of Jonscher's law: s(w) = sdc + Awn \sigma (\omega ){ } = {\sigma_{\rm{dc}}} + { }A{\omega^n} . The conductivity follows the Arrhenius relation. The variation of the value of these elements with temperatures confirmed
the availability of the phase transition at 343 K detected by DSC and electrical measurements. 相似文献
13.
Composite cathode material LiFePO4–Li3V2(PO4)3 is synthesized through a chemical reduction and lithiation using FeVO4·xH2O as both iron and vanadium sources. The structural properties of LiFePO4–Li3V2(PO4)3 are investigated. X-ray diffraction results show the composite material containing olivine type LiFePO4 and monoclinic Li3V2(PO4)3 phases. High-resolution transmission electron microscopy and energy-dispersive X-ray spectrometry results indicate that mutual
doping effects take place between the LiFePO4 and Li3V2(PO4)3 particles with V3+ doping the LiFePO4 while Fe2+ dopes the Li3V2(PO4)3. LiFePO4–Li3V2(PO4)3 nanocomposites are formed in the carbon webs. There is no structural compatibility between monoclinic (Li3V2(PO4)3) and olivine (LiFePO4) domains in composite material LiFePO4–Li3V2(PO4)3. 相似文献
14.
We present a simple and compact continuous-wave (CW) 1176 nm laser based on self-frequency Raman conversion in continuous-grown
YVO4/Nd:YVO4 composite crystal. With a composite crystal 30 mm in length, a maximum output power up to 1.84 W was achieved at the incident
diode pump power of 23.6 W. Corresponding to overall optical conversion, the efficiency was 7.8% and the slope efficiency
was 8.5%. The conversion efficiency has been doubled compared with the conventional Nd:YVO4 CW self-frequency Raman laser. The excellent performance of this laser shows that the long continuous-grown YVO4/Nd:YVO4 composite crystal is promising in the application of CW Raman lasers and ideal for miniaturization. 相似文献
15.
A new polyanionic cathode material, Li3V2(PO4)3·LiMn0.33Fe0.67PO4/C for lithium-ion batteries, was synthesized using a sol-gel method and with N,N-dimethyl formamide as a dispersion agent. The analysis of electron transmission spectroscopy and X-ray diffraction revealed that the composite contained two phases. The material has high crystallinity with a grain size of 20–50 nm. The valence states of Mn, V, and Fe in the composite were analyzed by X-ray photoelectron spectroscopy. The electrochemical kinetics in Li3V2(PO4)3 is effectively enhanced by the incorporation of LiMnPO4 and LiFePO4, via structure modification and reduced Li diffusion length. The Li3V2(PO4)3·LiMn0.33Fe0.67PO4/C materials displayed high rate capacity and steady cycle performance with discharge capacity remained 148 mAh g?1 after 50 cycles at the rate of 0.2C. In particular, the composite exhibited excellent reversible capacities, with the values of 157, 134, 120, 102, and 94 mAh g?1 at charge/discharge 0.2, 0.5, 1, 2, and 5C rates, respectively. 相似文献
16.
Kiichirou?Koyasu Wilko?Westh?user Marco?Niemietz Jan?Heinen Gerd?Gantef?r 《Applied Physics A: Materials Science & Processing》2009,96(3):679-684
Using time-resolved photoelectron spectroscopy, the decay channels of AuO2− and Au2O2− following photoexcitation with 3.1-eV photons have been studied. For AuO2−, a state with a rather long lifetime of 30 ps has been identified. Its decay path could not be determined but photodesorption
can be excluded. For Au2O2−, the spectra indicate O2 desorption after 3.1-eV photoexcitation on a time scale of 1 ps. While comparing these results on Au
n
O2− with analogous data on Ag
n
O2− clusters, a discernible pattern emerges: for dissociatively bound O2(AuO2−, Ag3O2−), there are long-living excited states which do not decay by oxygen desorption, while for molecular chemisorption (Au2O2−, Ag2O2−, Ag4O2−, Ag8O2−), the 3.1-eV photoexcitation triggers fast O2 desorption with a high quantum yield. 相似文献
17.
G. Wang X. Wang Y. Zhou Y. Chen C. Li Y. Zhu Z. Xu C. Chen 《Applied physics. B, Lasers and optics》2008,91(1):95-97
We obtained the second harmonic of a frequency-tripled Nd:YVO4 laser at wavelength of 177.3 nm with 12.95 mW output by using an optically contacted KBe2BO3F2-CaF2 prism-coupled device with a 2.1 mm thick KBe2BO3F2 crystal, which is to our knowledge the best result at this wavelength.
PACS 42.65.Ky; 42.70.Mp; 42.55.Xi 相似文献
18.
A high-power, continuous-wave 0.6% Nd3+-doped ceramic Y3Al5O12 (Nd:YAG) laser has been developed. 110 W laser output at 1064 nm was obtained, with a slope efficiency of about 41%. The M2 factor was found to be around 6. The laser performance of the ceramic laser material was found to compare favorably with that obtained with single crystal Nd:YAG. PACS 42.55.-f; 42.55.Xi; 42.70.Hj 相似文献
19.
S. Z. Li S. J. Luo R. Fu B. B. Jin K. F. Wang J.-M. Liu J. F. Ding X. G. Li 《Applied Physics A: Materials Science & Processing》2009,96(4):893-898
The terahertz dielectric response of LuFe2O4 is investigated by terahertz time-domain spectroscopy over a temperature range of 6–290 K. It is revealed that besides the
central mode associated with the charge-ordered state, a soft TO1 mode at below ∼240 K is identified indicating the existence of displacing ferroelectricity, in addition to the charge-ordering-induced
ferroelectricity at below 320 K. The anomaly of the soft mode at ∼180 K reflects the magnetoelectric correlation between the
soft TO1 mode and the spin/charge fluctuations revealed recently. Finally, the magnetic property at below ∼240 K is discussed. 相似文献
20.
The specific heat of [NH2(CH3)2]2ZnCl4 was measured calorimetrically in the temperature region 80–300 K. As the temperature T decreases, the C p (T) dependence indicates a phase transition sequence, with the phase transition at T6=151 K observed for the first time. The thermodynamic characteristics of the crystal were refined. The transformation occurring at T2=298.3 K is shown to be an incommensurate-commensurate phase transition. 相似文献