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1.
In this study, the effects of doping by 3d (V, Mn, Fe, Ni) and 4f (Nd, Sm, Er) ions on dielectric and infrared properties of SrTiO3 (STO) single crystals are investigated. It is well known that doping of the SrTiO3 can change the dielectric properties of the STO from an insulator to an n-type semiconductor, and even to a metallic conductor. Dielectric and infrared (IR) properties of the undoped STO and doped STO single crystals are analyzed using dielectric spectroscopy (80 kHz-5 MHz), transmission (200 cm^-1-4000 cm^-1), and reflection spectroscopy (50 cm^-1-2000 cm^-1). It is found that doping by the 3d ions reduces the value of dielectric permittivity, but the trend of temperature dependence of the dielectric permittivity remains almost unchanged. On the other hand, dielectric spectroscopy measurements for samples doped by 4f ions show the anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition. There are two fractures of temperature dependences of inverse dielectric permittivity εr^-1 (T). Transmittance spectroscopy measurements show that there are differences in the shape of the spectrum in the mid-IR region between the undoped STO and the one doped by 4f ions. The differences in the reflectance spectrum between the STO:Nd and STO are analyzed in detail.  相似文献   

2.
In ITER test blanket module design, the elucidation of tritium recovery from solid tritium breeding material is one of critical issues and Li2TiO3 is a candidate of tritium breeding materials. In the present study, in order to understand tritium behavior in solid breeding material Li2TiO3, the X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) experiments are carried out to elucidate the trapping behavior using 3 keV D2^+ implanted sample. The Ti-2p XPS spectrum shows that a shoulder appeared at the lower energy side as increasing ion fluence, and it was suggested that Ti^3+ was formed by the reduction of Ti^4+.  相似文献   

3.
A quasiclassical trajectory study with the sixth-order explicit symplectic algorithm for the N(^4S)+O2(X^3∑g^-) → NO(X^2Ⅱ) +O(^3P) reaction has been reported by employing a new ground potential energy surface. We have discussed the influence of the relative translational energy, the vibrational and rotational levels of O2 molecules on the total reaction cross section. Thermal rate constants at temperatures 300, 600, and 1000 K determined in this work for the reaction are 4.4 × 10^7, 1.8 × 10^10, and 3.1 × 10^11 cm^3mol^-1s^-1, respectively. It is found that they are in better agreement with the experimental data than previous theoretical values.  相似文献   

4.
Cross sections of electron-loss in H(1s)+ H(1s) collisions and total collisional destruction of H(2s) in H(1s) 4- H(2s) collisions are calculatted by four-body classical-trajectory Monte Caylo (CTMC) method and compared with previous theoretical and experimental data over the energy range of 4-100 keV. For the former a good agreement is obtained within different four-body CTMC calculations, and for the incident energy Ep 〉 10 keV, comparison with the experimental data shows a better agreement than the results calculated by the impact parameter approx- imation. For the latter, our theory predicts the correct experimental behaviour, and the discrepancies between our results and experimental ones are less than 30%. Based on the successive comparison with experiments, the cross sections for excitation to H(2p), single- and double-ionization and H- formation in H(2s)+H(2s) collisions are calculated in the energy range of 4-100 keV for the first time, and compared with those in H(1s)+H(1s) and H(1s)+U(2s) collisions.  相似文献   

5.
This paper reports that the transverse laser induced thermoelectric voltages (LITV) axe observed for the first time in the step flow growth (1- x)PD(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength, the largest induced voltage is observed in the 0.50Pb(Mg1/3Nb2/3)O3-0.50 PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.  相似文献   

6.
Three low-lying electronic states (X1∑, a3∑+, and A1II) of NO+ ion are studied using the complete active space self-consistent-field (CASSCF) method followed by highly accurate valence internally contracted multi-reference configuration interaction (MRCI) approach in combination of the correlation-consistent sextuple basis set augmented with diffuse functions, aug-cc-pV6Z. The potential energy curves (PECs) of the NO+(X1∑+, a3∑+, A1II) are calculated. Based on the PECs, the spectroscopic parameters Re, De, We, WeXe, ae, Be, and D0 are reproduced, which are in excellent agreement with the available measurements. By numerically solving the radial SchrSdinger equation of nuclear motion using the Numerov method, the first 20 vibrational levels, inertial rotation and centrifugal distortion constants of NO+(X1∑+, a3∑+, A1II) ion are derived when the rotational quantum number J is equal to zero (J = 0) for the first time, which accord well with the available measurements. Finally, the analytical potential energy functions of these states are fitted, which are used to accurately derive the first 20 classical turning points when J = 0. These results are compared in detail with those of previous investigations reported in the literature.  相似文献   

7.
We investigate the giant magnetoresistance of composites (La1-xAgzMnO3)1-υ(MnO2/Mn2O3)υ. The magnetoresistive property of the composites shows the characteristics of intergranular tunnelling. A conductivity leap has been observed around y = 0.7. The composite (La0.926Ag0.074MnO3)0.698(MnO2/Mn2O3)0.302 has been found to show the greatest magnetoresistance in the samples. Its room-temperature MR ratio reaches 24% under a field of 1.8T. These phenomena suggest a percolation transformation and a kind of field-induced fluctuation in percolation in the samples investigated.  相似文献   

8.
By applying systematically enlarged multi-configuration Dirac-Fock wavefunction, the transitions for electricdipole allowed (E1) and forbidden (E2, M1 and M2) lines are studied among 4f pair coupling and low-lying configurations for singly ionized nitrogen. Most important effects of relativity, electron correlation, the rearrangement of electron density, Breit interaction, and quantum electrodynamic effects are included in the computation. Then, allowed (E1) and forbidden (E2, M1 and M2) transition probabilities of 4f for N+ are obtained and compared with experimental results. Good agreement with available experimental results is found and most of the data of 4f are presented for the first time.  相似文献   

9.
By using a pump-probe technique, the nascent rotational and vibrational state distributions of CsH are obtained in the Cs(6^2 D,7^2 D) plus H2 reaction. The nascent CsH molecules are found to populate the lowest two vibrational (v″ = 0 and 1) levels of the ground electronic state. By comparing the spectral intensities of the CsH action spectra with those of pertinent Cs atomic fluorescence excitation spectra, the relative reactivity with 1-12 is in an order of6^2D3/2 〉 6^2D5/2 〉 7^2D3/2 〉 7^2D5/2. The rotational temperatures are found to be slightly below the cell temperature. The relative fractions (〈fV〉, 〈fR〉, 〈fT〉) of average energy disposal are derived as (0.2,0.12,0.68), (0.2,0.12,0.68), (0.07,0.04,0.89) and (0.07,0.04,0.89) for the 6^2D3/2, 6^2D5/2, 7^2D3/2 and 7^2D5/2, respectively. The major available energy is released as translation. These results support that the reaction mechanism of Cs(6^2 D,7^2 D) plus 112 is primarily a eollinear abstraction and not an insertion.  相似文献   

10.
We examine RCoO3 (R=La, Ce, Pr, Nd, Sin, Eu, Gd, and Dy) perovskites prepared with the solid-state reaction method by Raman spectroscopy, and report the Raman active phonons in the RCoO3 perovskites crystallized in cubic symmetry for RCoO3 (R=La, Ce, Pr and Nd) and orthorhombic symmetry for RCoO3 (R=Sm, Eu, Gd, and Dy). It is found that the Raman spectra of RCoO3 perovskites are strongly dependent on the ionic radius of the rare earth elements, and the frequency shift of the most intense modes of the orthorhombic samples are correlated with some structural parameters such as Co-O bond distances, ionic radius of the rare earth elements and Jahn-Teller distortion. It is clear that Raman spectroscopy has the advantage of sensitivity to structure distortion and oxygen motion.  相似文献   

11.
Polarization hysteresis loops, x-ray diffraction and temperature dependent dielectric constant under different electric fields for <110> oriented 0.7PMN-0.3PT crystals are measured. The field-induced phase transition and the process of depolarization are discussed. The results show that with the electric field E increasing, the single-crystal form changes from the relaxor state of rhombohedral to normal rhombohedral, then to a monoclinic state via polar-axis reorientation and polarization rotation. Orthorhombic phase may present when E≥10kV, but it is an unstable form after E removal. The depolarization process is not just the reversal of the polarization process. It is noticed that only the temperature-dependent dielectric behaviour is not enough to judge the processes of the E-field induced phase transition.  相似文献   

12.
Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems.  相似文献   

13.
We discuss the influence of Al^3+ on the charge transfer state (CTS) and the photoluminescence properties of BaZr(BO3)2:Eu. The results reveal that there is a red shift which is about 20nm for the charge transfer state when doping with Al^3+ and indicate the formation of ‘free' electrons due to the change of microstructures. In addition, the influence or Al^3+ doping on the PPR is analysed and a new explanation is raised based on the photo luminescent mechanism. It is the CTS intensity rather than the CTS energy that influences the peak-peak ratio.  相似文献   

14.
With iodine vapour treatment of various single crystals of Bi-Sr-Ca-Ln(Rare earch element)-Cu-O system, the stage-1 iodine-intercalation compounds of Bi2(Sr,Nd)2CuOy(2201), Bi2Sr2(Ca,Gd)Cu2Oy or Bi2Sr2CaCu2Oy(2212) and Bi8SrCaO14 have been prepared. x-ray diffraction and transmission electron microscope analysis indicate that iodine layer of thickness 3.2~3.5Å is formed between two Bi2-O2  相似文献   

15.
M. Ö  ztas  M. Bedir  Z. Ö  ztürk  D. Korkmaz  S. Sur 《中国物理快报》2006,23(6):1610-1012
In2S3 nanocrystalline films are prepared on glass substrates by the spray pyrolysis technique using indium chloride and thiourea as precursors. The deposition is carried out at 350°C on glass substrates. The films are then annealed for two hour at 200, 400, 600, and 800°C in O2 flow. This process allows the transformation of nanocrystal In2O3 films from In2S3 films and the reaction completes at 600°C. These results indicate that the In2O3 film prepared by this simple thermal oxidation method is a promising candidate for electro-optical and photovoltaic devices.  相似文献   

16.
New lead-free ceramics (Lio.12Na0.88) (Nbo.9-x Ta0.10 Sbx) 03 (0.01 × 0.06) are synthesized by solid-state reaction method. The dielectric, piezoelectric and ferroelectric properties of the ceramics are studied. The dielectric constant dependence with temperature and frequency of the ceramic specimen with x = 0.04 shows typical characteristics of relaxor ferroelectrics, and the Vogel-Fulcher relationship is fulfilled. The dielectric behaviour and its relation to the phase transition phenomena are discussed. The polarization hysteresis loops at room temperature are also measured.  相似文献   

17.
The resistivity of the heavy-doped La1/3Ca2/3MnO3 (LCMO) is simulated using a random resistor network model, based on a phase separation scenario. The simulated results agree well with the reported experimental data, showing a transition from a charge-disordered (CDO) state embedded with a few ferromagnetic (FM) metallic clusters to a charge-ordered (CO) state, corresponding to the transition from a high-temperature paramagnetic (PM) insulating state to a low-temperature antiferromagnetic (AF) insulating state. Furthermore, we find that the number of AF/CO clusters increases with decreasing temperature, and the clusters start to connect to each other around 250K, which causes percolating in the system. The results further verify that phase separation plays a crucial role in the electrical conductivity of LCMO.  相似文献   

18.
YBa2Cu4O8/La0.67Ca0.33MnO3/YBa2Cu4O8(YBCO/LCMO/YBCO) trilayer films were prepared by magnetron facing-target sputtering. For the first time, the oscillatory behaviour of superconducting transition temperature Tc,ON with the thickness of LCMO (dL) has been observed. The strongest nonmonotonic information in the Tc,ON--dL curves appears clearly when dL is larger than the critical thickness dLCR. The metal--semiconductor transition temperature can only be detected at dL>dLCR. The dependence on the ferromagnetic spacer layer in YBCO/LCMO/YBCO systems suggests strongly the interplay of ferromagnetic and superconducting couplings.  相似文献   

19.
La0.67Ca0.33MnO3/Alq3/Co sandwiched-structure organic spin valves are fabricated by vacuum thermal evaporation method. A giant magnetoresistance (GMR) of 14% is observed at low temperature 100K. At 30K, the magnetoresistance can increase to 50%. The large GMR of the device is attributed to the high spin polarization and low conductivity of the La0.67Ca0.33MnO3 contact. The magnetoresistance ΔR/R and the coercive field of the Co electrode depend strongly on temperature. The large high-field magnetoresistance reported on La0.67Sr0.33MnO3/Alq3/Co organic spin valves [Nature 427 (2004) 821] is not observed in our La0.67Ca0.33MnO3/Alq2/Co organic spin valves.  相似文献   

20.
Effect of Fe3O4 segregation at grain boundaries on the electrical transport and magnetic properties of La0.67Ca0.33MnO3 is investigated. The experimental results show that the Fe3O4 segregation not only shifts the paramagnetic-ferromagnetic transition temperature of La0.6TCa0.33MnO3 to a lower temperature region but also induces a new transition in a lower temperature region. Meanwhile, the transition processes observed in both the resistivity and magnetization curves are obviously widened. Compared to pure La0.67Ca0.33MnO3, we assume that the Fe3O4 segregation level at the grain boundaries can modify the electrical transport and magnetic properties of La0.67Ca0.33MnO3.  相似文献   

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