共查询到20条相似文献,搜索用时 15 毫秒
1.
K.V. Ivanovskikh A. Meijerink A. Speghini C. Ronda M. Bettinelli 《Journal of luminescence》2010,130(5):893-16384
The silicates Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12, both undoped and doped with Pr3+ ions, have been synthesized by solid-state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only Ca3Sc2Si3O12:Pr3+ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of Ca3Y2Si3O12:Pr3+ and Ca3Lu2Si3O12:Pr3+ show features attributed to emission from two distinct sites accommodating the Pr3+ dopant. The decay kinetics of the Pr3+ 5d-4f emission in Ca3Sc2Si3O12:Pr3+ upon VUV excitation across the band gap are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow components are attributed to defect luminescence. 相似文献
2.
Bi1.5Zn1.0Nb1.5O7/Ba0.6Sr0.4TiO3/Bi1.5Zn1.0Nb1.5O7 tunable multilayer thin film has been fabricated by pulsed laser ablation and characterized. Phase composition and microstructure of multilayer films were characterized by X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film has very smooth surface with RMS roughness of 1.5-2 nm and grain size of 100-150 nm. Total film thickness has been measure to be 375 nm. The BZN thin films at 300 K, on Pt(1 1 1)/SiO2/Si substrate showed zero-field dielectric constant of 105 and dielectric loss tangent of 0.002 at frequency of 0.1 MHz. Thin films annealed at 700 °C shows the dielectric tunability of 18% with biasing field 500 kV/cm at 0.1 MHz. The multilayer thin film shows nonferroelectric behavior at room temperature. The good physical and electrical properties of multilayer thin films make them promising candidate for tunable microwave device applications. 相似文献
3.
4.
5.
A. I. Burkhanov Yu. V. Kochergin K. Bormanis A. Kalvane M. Dambekalne 《Physics of the Solid State》2009,51(7):1475-1477
The influence of the prehistory on the electrical properties of layered ferroelectrics is investigated. It is established
that the heating of short-circuited samples of the nonpolarized ceramic material Na0.5Bi8.5Ti2Nb4O27 leads to the appearance of maxima of the current at temperatures below the Curie point only in the case of preliminary ageing
of the samples.
Original Russian Text ? A.I. Burkhanov, Yu.V. Kochergin, K. Bormanis, A. Kalvane, M. Dambekalne, 2009, published in Fizika
Tverdogo Tela, 2009, Vol. 51, No. 7, pp. 1393–1394. 相似文献
6.
H. Gamari-Seale I.O. Troyanchuk K.L. Stefanopoulos 《Physica B: Condensed Matter》2008,403(17):2924-2929
In this paper we report the study of the perovskites La0.7Ca0.3Mn0.5Co0.5O3 and La0.8Sr0.2Mn0.5Co0.5O3 by neutron powder diffraction at various temperatures and magnetization measurements in zero applied field and at low cooling regimes. The replacement of half Mn by Co in La0.7Ca0.3MnO3 and La0.8Sr0.2MnO3 destroys their long-range ferromagnetism exhibiting a cluster glass ferromagnetic order similar to the one observed in many cobaltites. 相似文献
7.
D. Johnson P. Peeters V. Verbuere E. De Wolf W. Dunwoodie G. Grammatikakis Y. Goldschmidt-Clermont A. Stergiou F. Grard V.P. Henri P. Herquet J. Schlesinger R. Windmolders V. Kubik V. Yarba 《Nuclear Physics B》1976,115(2):195-207
The cross sections for the reactions: (a) K+p → K+pπ+π?π+ and (b) K+p → K+π+π+π?n have been determined at 8.2 and 16 GeV/c with the following results:at 8.2 GeV/c: (a) 0.99 ± 0.07 mb, (b) 0.41 ± 0.04 mb;at 16 GeV/c: (a) 0.72 ± 0.05 mb, (b) 0.28 ± 0.05 mb.Using the available data at other energies, the cross-section dependence of these reactions on the incident momentum is discussed. 相似文献
8.
An experimental study of proximity effect in La0.67Sr0.33MnO3-YBa2CU3O7-La0.67Sr0.33MnO3 trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I
c) as the thickness of La0.67Sr0.33MnO3 layers (d
F) is scanned from ∼50 ? to ∼ 1100 ?. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures,
this observation suggests a long range proximity effect in the manganite, modulated by its weak exchange energy (∼2 meV).
The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d
F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.
相似文献
9.
J. J. Lin W. Y. Lin R. F. Tsui 《Physica C: Superconductivity and its Applications》1993,210(3-4):455-462
We have measured the resistivities of Al2O3-Bi2Sr1.8Ca1.2Cu2Oy and MgO-Bi2Sr1.8Ca1.2Cu2Oy composites with the nominal Bi2Sr1.8Ca1.2Cu2Oy volume fraction, 2212, ranging from 0.15 to 1.00. For the Al2O3-Bi2Sr1.8Ca1.2Cu 2Oy composites, we find for the samples with 2212≥0.6 that the superconducting transition temperature, Tc, is not disturbed by the addition of Al2O3. For 2212<0.3, no zero-resistivity state is observed. For the MgO-Bi2Sr1.8Ca1.2Cu2Oy composites, Tc is barely disturbed for the samples with ρ2212≥0.7. No superconducting state is observed for the samples with ρ2212<0.35. The variation of (300 K) with ρ2212 indicates a three-dimensional percolating Bi-Sr-Ca-Cu-O matrix occurring at ρ2212≈0.19 and ≈0.15 in Al2O3-Bi2Sr1.8Ca1.2 Cu2Oy and MgO-Bi2Sr1.8Ca1.2Cu2Oy, respectively. Both resistivity and magnetization measurements suggest that the reactions of Bi2Sr1.8Ca1.2Cu2Oy with MgO are weaker than with Al2O3. 相似文献
10.
H.-J. Behrend J. Bürger L. Criegee H. Fenner J.H. Field G. Franke J. Meyer V. Schröder H. Sindt U. Timm G.G. Winter W. Zimmermann P.J. Bussey A.J. Campbell J.B. Dainton D. Hendry G. McCurrach J. Grunhaus 《Physics letters. [Part B]》1985,158(6):536-542
The reactions e+e?→μ+μ?γ and e+e?→e+e?γ have been studied with the CELLO detector at the PETRA storage ring. Data have been collected from . In a Dalitz plot analysis of the data, good agreement is found with QED, except for the region Mxμγe>0.8 where the probability that QED describes the high energy data is at the percent level. 相似文献
11.
Dominik Uhlich 《Journal of luminescence》2008,128(10):1649-1654
This work reports on the phase formation during a solid-state reaction of Eu3+-doped garnets with the general formula A3B2Ge3O12 (A=Ca, Sr and B=Ga, In, Y) and their luminescent properties. It is shown by XRD and DTA/TG experiments that the garnet-phase formation is completed at 1100-1200 °C. Moreover, it turned out that the position of the oxygen to europium charge-transfer band and the intensity of the forbidden 4f-4f transitions of Eu3+ is dependent on the covalent interaction between the Eu3+ activator and the surrounding oxygen anions. The investigated red-emitting luminescent materials show high lumen equivalents and deep red emission at the same time, which makes them attractive for the application in LEDs (light emitting diodes), in particular for near UV-emitting LEDs. 相似文献
12.
R.Z. Mehdiyeva Mir Hasan Yu. Seyidov I.B. Baykulov 《Journal of Physics and Chemistry of Solids》2006,67(12):2623-2627
Boundaries of morphotropic phase transitions region in the system of solid solutions K2Pb4Nb10O30-Na2Pb4Nb10O30-K6W4Nb6O30 with the structure of the tetragonal tungsten bronze have been specified. Presence of the second morphotropic phase transition, perpendicular to the first one has been revealed. The temperature dependences of the structural parameters of some compounds have been investigated. The compounds with high values of Curie temperatures and working temperatures have been obtained. 相似文献
13.
Incommensurate modulations in Ba2TiSi2O8, Sr2TiSi2O8, and Ba2TiGe2O8 are compared based on their corresponding electron diffraction patterns. The dependence of the modulations on chemical composition provides a suitable model system for the investigation of incommensurations in framework structures using high-resolution transmission electron microscopy (HRTEM). A widening of quantitative HRTEM utilising the concept of rigid units is proposed allowing for a determination of atomistic displacements responsible for the formation of incommensurately modulated structures. 相似文献
14.
Ghislain Blanquet Jacques Walrand Charles P. Courtoy André Fayt 《Journal of Molecular Spectroscopy》1980,81(2):473-479
The ν3 fundamental of OCS has been measured with a resolution of about 0.03 cm?1 for the isotopic species 16O12C34S and 16O13C34S. The associated transition 0111-0110 has also been measured. The transition 1001-0000 is also reported for the 16O12C34S species. 相似文献
15.
The hot band system ν9 + ν11 ? ν11, ν10 + ν11 ? ν11 in allene-d4 was studied at a resolution near 0.010 cm?1. About 1500 partly overlapped hot band rotational lines were assigned and fitted to a model taking into account z-Coriolis resonance between the combination levels ν9 + ν11 and ν10 + ν11 as well as vibrational l-type resonances within these levels. Upperstate constants have been derived from an analysis in which the constants for the ν11 level were constrained. A detailed study of rotational as well as vibrational l-type doublings occurring in the KΔK = ?1 subband is presented, and the sign of vibrational l-type doubling constants for the ν10 + ν11 level is determined. A localized (x, y)-Coriolis resonance between ν10 + ν11 and ν4(B1) + ν11 is discussed and the interaction parameter is obtained as well as some constants for ν4 + ν11. 相似文献
16.
Guangtao Wang Minping Zhang Lihua Zheng Zongxian Yang 《Solid State Communications》2011,151(18):1231-1235
The electronic structure and magnetic properties of new layered oxyselenide compounds La2O3Fe2Se2 and La2O3Co2Se2 are studied by first-principles calculations. Our results indicate that both compounds are Mott-insulators with orbital ordering. The ground states of both compounds are the checkerboard antiferromagnetic states, which are different from the iron pnictide superconductors, although their structures are similar to those of the Fe-As-based superconductors. 相似文献
17.
D.V. Bugg 《Physics letters. [Part B]》1974,52(1):102-104
Recent data on the reaction show four conspicuous dips in the angular distribution at fixed values of ν = t?u. The conjecture is made that the channel π?π+ → π?π+ has zeros at the same ν values. Using data of the CERN-Munich group, one can follow the zeros through the whole Mandelstam plane. The zeros pass through the intersections of s and t channel poles, as the Veneziano model predicts; however, away from these intersections, they propagate in a fashion systematically quite different from Veneziano's ansatz. 相似文献
18.
Marcel Snels 《Journal of Molecular Spectroscopy》2004,224(1):13-17
The infrared spectrum of isotopically pure CH279BrCl has been recorded at a resolution of 0.0023 cm−1 (FWHM) in the range 550-800 cm−1 with a Bruker IFS 120 HR Fourier transform spectrometer in Wuppertal. Here we report the full rotational analysis of the ν4 and ν5 fundamentals and of the hot-bands ν4+ν6−ν6 and ν5+ν6−ν6. Ground state combination differences were constructed for all bands, yielding improved ground state constants, up to quartic terms, as well as reliable rotational constants for the ν4, ν5, and ν6 states. 相似文献
19.
Aldée Cabana Michel Laurin Claude Pépin Walter J. Lafferty 《Journal of Molecular Spectroscopy》1976,59(1):13-27
The infrared absorption spectrum of the ν3 band of 14NO2 has been recorded with a resolution and a frequency accuracy much improved over the previous investigations. The K- and N-line assignments have been greatly extended and a more accurate set of spectroscopic constants derived. Several lines in the subbands with Ka ≥ 3 have been observed to be doubled by spin-rotation interaction and spin-rotation interaction constants have been obtained. Several weak series of lines in the spectrum (Ka = 0, 1, 2, and 3) have been unambiguously assigned to the “hot band” ν2 + ν3 ? ν2. Lines of the Ka = 3, 4, 5, and 6 sub-bands of ν3 have been found to be perturbed by a Coriolis interaction with the Ka = 4, 5, 6, and 7 levels of 2ν2. 相似文献
20.
Attempts have been made to synthesize a few compositions Ce0.80La0.15Al0.05O1.90, Ce0.80Sm0.10Gd0.05Al0.05O1.90, and Ce0.80Gd0.10Sm0.05Al0.05O1.90 by citrate–nitrate auto-combustion method. The aim of the present investigation was to study the effect of co-doping and
multiple doping on the ionic conductivity of CeO2 for its use as solid electrolyte in intermediate temperature solid oxide fuel cells. XRD patterns showed that all the samples
have fluorite-type crystal structure similar to undoped ceria. Microstructures of thermally etched samples have been studied
by scanning electron microscopy. Contributions of grains σ
g and grain boundaries σ
gb to the total conductivity σ
T, have been determined using impedance analysis. Impedance measurements were made in the frequency range 1 Hz–1 MHz and temperature
range 250–500 °C. Our experimental results show that multiple doping is more effective than co-doping for improving the oxide
ion conductivity of ceria in the materials investigated in the present study. 相似文献