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1.
《Journal of magnetism and magnetic materials》1987,66(3):323-324
The photoacoustic absorption spectrum of vanadium-doped CePO4 samples has been observed at room temperature. Two absorption peaks are seen, one at 11200 cm-1 and another at 14800 cm-1. They are attributed to VO2+ ions in interstitial sites of distorted octahedral symmetry. 相似文献
2.
Inverted organic solar cells with solvothermal synthesized vanadium-doped TiO_2 thin films as efficient electron transport layer
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Mehdi Ahmadi Sajjad Rashidi Dafeh Samaneh Ghazanfarpour Mohammad Khanzadeh 《中国物理 B》2017,26(9):97203-097203
We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO_2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly(3-hexylthiophene) P3HT:[6-6] phenyl-(6) butyric acid methyl ester(PCBM). 1% vanadium-doped TiO_2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO_2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO_2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO_2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO_2 thin film showed slightly higher power conversion efficiency and great J_(sc) of 10.7 mA/cm~2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO_2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO_2 thin film was better in all wavelengths. 相似文献
3.
A study is reported of the temperature dependences of the dc and ac electrical conductivities, as well as of I–V characteristics of pure and vanadium-doped germanosillenite crystals. It has been established that the charge carriers in Bi12GeO20 are electrons and holes. Doping with vanadium gives rise to a strong dependence of the conductivity and its activation energy on the dopant concentration. Within the model, the results explain the hopping-charge transfer in doped, closely compensated semiconductors. 相似文献
4.
Using the standard solid-state reaction method, several vanadium-doped ferroelectric ceramics of type SrBi4−x/3Ti4−xVxO15 (SBTV−x) were synthesized. The vanadium doping content, x, rangs from 0.00 to 0.06. The crystal structure of SrBi4Ti4O15 is not affected by V-doping. The electric breakdown voltage of the samples increases with V content. Meanwhile, V-doping results in a notable enlargement of remnant polarization (2Pr). The 2Pr of STBV−0.03 reaches a very large value, which is over 50 μC/cm2 and is nearly twice greater than that at zero doping. The Curie temperatures of V-doped samples decrease slightly in comparison with that of SrBi4Ti4O15. V-doping can improve the electric properties of SrBi4Ti4O15 without sacrificing its thermal stableness. 相似文献
5.
Using the standard solid-state reaction method, several vanadium-doped ferroelectric ceramics of type SrBi4−x/3Ti4−xVxO15 (SBTV-x) were synthesized. The vanadium doping content, x, ranges from 0.000 to 0.06. The crystal structure of SrBi4Ti4O15 is not affected by V-doping. The electric breakdown voltage of the samples increases with V content. Meanwhile, V-doping results in a notable enlargement of remnant polarization (2Pr). The 2Pr of STBV-0.03 reaches a very large value, which is over 50 μC/cm2 and is nearly twice greater than that at zero doping. The Curie temperatures of V-doped samples decrease slightly in comparison with that of SrBi4Ti4O15. V-doping can improve the electric properties of SrBi4Ti4O15 without sacrificing its thermal stableness. 相似文献
6.
Hao Lin Yanwei Wen Chenxi Zhang Lulu Zhang Yunhui Huang Bin Shan Rong Chen 《Solid State Communications》2012,152(12):999-1003
Recent experiments showed beneficial influence of vanadium doping on the electrochemical performance of lithium iron phosphate (LiFePO4) cathode materials. First-principles calculations have been performed to investigate the stability, electronic structure and lithium diffusivity of vanadium-doped LiFePO4 and to elucidate the origin of such improvement. It is found that vanadium prefers occupying Fe sites and leads to additional density of states within the intrinsic bandgap. By the nudged elastic band method, we show that the barrier of Li ions diffusion along the one dimensional channel in both LiFePO4 and FePO4 phases can be effectively reduced by vanadium doping. Structural analysis shows the lower diffusion barrier ties closely to a volumetric expansion of the diffusion channel. 相似文献
7.
Two kinds of vanadium-doped TiO2 powders photocatalysts were prepared by sol-gel method in even doping and uneven doping modes, and were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of TiO2 photocatalysts doped by vanadium evenly with lower dopant level up to 0.002 mol.% is better than that of undoped TiO2, while with higher dopant level the activity is worse. TiO2 photocatalysts doped by vanadium unevenly with a p-n junction semiconductor structure, was shown to have a much higher photocatalytic destruction rate than that of TiO2 photocatalysts doped by vanadium evenly and undoped TiO2, which is ascribed mainly to the electrostatic-field-driven electron-hole separation in TiO2 particles doped by vanadium unevenly. 相似文献
8.
R. Montenegro A. Shumelyuk R. Kumamoto J. F. Carvalho R. C. Santana J. Frejlich 《Applied physics. B, Lasers and optics》2009,95(3):475-482
Holographic recording in a vanadium-doped B12TiO20 (BTO) photorefractive crystal puts into evidence a large hole–electron competition showing a fast and a slow hologram components.
From the fast component evolution, some material parameters for the electron-donor photoactive centers are computed. The wavelength-resolved
photoconductivity is shown to be strongly modified by V-doping compared to undoped and doped BTO with other elements. The
increase of photoconductivity by green light preexposure is almost negligible here if compared with undoped BTO. Activation
energy for dark conductivity measured for BTO:V is similar to that for undoped BTO, as measured close to room temperature,
but sensibly lower than the value reported in the literature for a much higher temperature range. Optical absorption and EPR
spectra do confirm already published results and suggestions about the possible role of vanadium in the sillenite structure. 相似文献
9.
Thuy-Duong Nguyen-PhanMyoung Bock Song Hyunran YunEui Jung Kim Eun-Suok OhEun Woo Shin 《Applied Surface Science》2011,257(6):2024-2031
A series of vanadium-doped mesoporous titania with different metal contents was synthesized in the study via a sol-gel process with the assistance of a dodecylamine surfactant. The existence of vanadium ions not only suppressed crystallization and sintering but also enhanced the porosity of the mesoporous TiO2. Varying the vanadium concentration led to significant changes in the chemical oxidation state of each component. The presence of metal dopants significantly improved the removal efficiency of benzene and the doping the titania with 5 mol% vanadium removed the most benzene, regardless of the adsorption temperature. The adsorption behavior was elucidated by the specific surface area, the interactions between surface hydroxyl groups and the π-electrons of benzene, and the formation of σ-bonding and d-π* back-donation between the adsorbent and organic compounds. 相似文献
10.
Kai-Huang Chen Chia-Hsiung Chang Chien-Min Cheng Cheng-Fu Yang 《Applied Physics A: Materials Science & Processing》2009,97(4):919-923
We report the enhancement of ferroelectric properties in vanadium-doped Bi4Ti3O12 (BIT) thin films prepared by rf magnetron sputtering method for MFM and MFIS structures. The optimal sputtering parameters
of the as-deposited Bi3.9Ti2.9V0.08O12 (BTV) ferroelectric films for different depositing times were obtained. Compared to the undoped BIT, vanadium doped BIT (BTV)
showed better physical and electrical characteristics. The as-deposited BTV showed a remanent polarization (2P
r
) of 23 μC/cm2, higher than the value of 16 μC/cm2 for BIT, as the measured frequency was 100 kHz. For BTV thin films in the MFIS structure, the leakage current density and
the memory window decreased, the change ratio of capacitance critically increased as the depositing time increased from 30
to 120 min. Regarding the measured physical properties, the micro-structure and thickness of as-deposited undoped and vanadium
doped BIT thin films were obtained and compared by XRD patterns and SEM images. 相似文献
11.
Metal organic chemical vapor deposition (MOCVD) has been used to grow vanadium-doped GaN (GaN:V) on c-sapphire substrate using VCl4 as the V source. The as-grown GaN:V exhibited a saturated magnetic moment (Ms) of 0.28 emu/cm3 at room temperature. Upon high-temperature annealing treatment at 1100 °C for 7 min under N2 ambient, the Ms of the GaN:V increased by 39.28% to 0.39 emu/cm3. We found that rapid thermal annealing leads to a remarkable increase in surface roughness of the V-doped GaN as well as the electron concentration. The annealing also leads to a significant increase in the Curie temperature (TC), we have identified Curie temperatures about 350 K concluded from the difference between the field-cooled and zero-field-cooled magnetizations. Structure characterization by x-ray diffraction indicated that the ferromagnetic properties are not a result of secondary magnetic phases. 相似文献
12.
Undoped and vanadium-doped Zn2SiO4 particles embedded in silica host matrix were prepared by a simple solid-phase reaction after the incorporation of ZnO and ZnO:V nanoparticles, respectively, in silica monolith using the sol–gel method with supercritical drying of ethyl alcohol in two steps. After supercritical drying and annealing in the temperature range between 1423 and 1473 K in an air atmosphere, the photoluminescence (PL) measurements show a band centered at about 760 nm in the case of non-doped Zn2SiO4 which is attributed to energy transfer from Zn2SiO4 particles to NBOHs interface defects. In the case of vanadium doped Zn2SiO4, the PL reveals a band centered at about 540 nm attributed to the vanadium in the interfaces between Zn2SiO4 particles and SiO2 host matrix. Photoluminescence excitation (PLE) measurements show different origins of the emission bands. The PLE band (~240–350 nm) may be understood as an energy transfer process from O2? to V5+ which occurs intrinsically in the vanadyl group. 相似文献
13.
R. V. S. S. N. Ravikumar K. Kayalvizhi A. V. Chandrasekhar Y. P. Reddy J. Yamauchi K. Arunakumari P. S. Rao 《Applied magnetic resonance》2008,33(1-2):185-195
Electron paramagnetic resonance (EPR) and optical studies have been carried out on Cu(II)-, VO(II)- and Cr(III)-doped strontium
tetraborate glasses to understand the distortion and substitution of these ions. The EPR results of Cu(II) glass indicate
that g
∥ > g
⊥, typical for the tetragonally elongated octahedral site of the Cu(II) impurity. The evaluated covalency parameter 0.788 suggests
a moderate covalency for the bonding. By correlating EPR and optical results, the in-plane π-bonding β1
2 is evaluated as 0.715. In the vanadium-doped glasses, the distortion must be a tetragonally elongated octahedron, similar
to Cu(II). However, the EPR studies show that g
⊥ > g
∥ indicating the tetragonally compressed octahedral site for the ion. The site symmetry is C
4V. Supported by the optical absorption, evaluated parameters propose a moderate covalency. The EPR and optical results for
Cr(III) glass indicate the distorted octahedral site symmetry in the host lattice. These results further suggest that the
bonding between Cr(III) and the ligands is covalent.
Authors' address: Renduchintala V. S. S. N. Ravikumar, Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar
522510, India 相似文献
14.
Ke ChenJingyi Li Wenxi WangYumin Zhang Xiaojing WangHaiquan Su 《Applied Surface Science》2011,257(16):7276-7285
The photodegradation of sulforhodamine B on vanadium-doped TiO2-montmorillonite (TiO2-MMT) nanocomposites was investigated under visible light irradiation. V-TiO2-MMT nanocomposites with different amounts of MMT were prepared by a sol-gel process. The microstructure and properties of V-TiO2-MMT were characterized by XRD, TEM, XPS, DRS, nitrogen adsorption isotherms, and FTIR. These analytic results indicated that the different Ti/MMT ratios exerted a great influence on their microstructures and their photocatalytic activities. The average sizes of V-TiO2-MMT were smaller than those of pure TiO2 and V-TiO2. And the layered structure of MMT was completely destroyed in the V-TiO2-MMT with the relatively high ratio of Ti/MMT (240, 120, 80, 60 mmol/g), but it retained the partial MMT layered structure and had an enlargement of some basal space of MMT in V-TiO2-MMT with the relatively low ratio of Ti/MMT (30, 24 mmol/g). V-TiO2-MMT/120 (120 denotes the ratio of Ti/MMT is 120 mmol/g. The names of other catalysts followed the same convention.) and V-TiO2-MMT/30 had relatively higher photocatalytic activity in comparison to the others. Besides, in the preparation process, we selected V-TiO2-MMT/120 using different washing media to examine the effect of washing medium on the photocatalytic activity. The result indicated that it was critical to choose a proper washing medium to obtain an optimal photocatalytic activity. 相似文献
15.
J. C. Launay V. Mazoyer M. Tapiero J. P. Zielinger Z. Guellil Ph. Delaye G. Roosen 《Applied Physics A: Materials Science & Processing》1992,55(1):33-40
We present new results on the growth of semi-insulating vanadium-doped cadmium telluride crystals and their characterization by different optical techniques such as photoinduced current transient spectroscopy, absorption, photoconductivity spectra, and photorefractive wave mixing. Our joint research program aims at developing optimized crystals for efficient optical processing in the near infrared through the photorefractive effect. 相似文献
16.
A series of vanadium-doped lithium niobate crystals was grown and their photorefractive properties were investigated with a 532 nm laser. At a total light intensity of 471 mW/cm(2), a short response time of only 0.57 s was achieved for 0.1 mol.% vanadium in LiNbO(3). The photorefractive process is dominated by the diffusion field instead of the photovoltaic field. The dominant charge carriers are electrons. The possible mechanism for the fast photorefractive response is discussed. 相似文献
17.
P. Kamiński R. Koz?owski M. Miczuga M. Paw?owski M. Kozubal J. ?elazko 《Opto-Electronics Review》2009,17(1):1-7
Photoinduced transient spectroscopy (PITS) has been applied to study electronic properties of point defects associated with
charge compensation in semi-insulating (SI) 6H-SiC substrates. The photocurrent relaxation waveforms were digitally recorded
in a wide temperature range of 20–800 K and in order to extract the parameters of defect centres, a two-dimensional analysis
of the waveforms as a function of time and temperature has been implemented. As a result, the processes of thermal emission
of charge carriers from defect centres were seen on the spectral surface as the folds, whose ridgelines depicted the temperature
dependences of emission rate for detected defect centres. The new approach was used to compare the defect levels in vanadium-doped
and vanadium-free (undoped) SI 6H-SiC wafers. 相似文献
18.
We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol–gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10 at.% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterised by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500 °C in air, the powder with an average particle size of 25 nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed. 相似文献
19.
We have recorded and investigated the ESR spectrum of vanadium-doped α-RbTiOPO4 single crystals in the temperature interval 77–300 K. Two types of structurally distinct centers, V1 and V2, with a 4:1 ratio
of the peak intensities were observed. The angular dependences of the resonance magnetic fields are described by a spin Hamiltonian
corresponding to axial symmetry with the parameters g
∥1=1.9305, g
⊥1=1.9565, A
∥1=−168.2×10−4cm−1, and A
⊥1=−54.3×10−4cm−1 for V1 centers and g
∥2=1.9340, g
⊥2=1.9523, A
∥2=−169.0×10−4cm−1, and A
⊥2=−55.2×10−4cm−1 for V2 centers. A model of a paramagnetic center is proposed: The vanadium ions replace titanium ions in two structurally
distinct positions Ti1 and Ti2 (V1 and V2 centers, respectively). The possibility that a VO2+ ion forms when α-RbTiOPO4 crystals and crystals of the KTP group (KTiOPO4, NaTiOPO4, α-and β-LiTiOPO4), studied earlier, are doped with vanadium is discussed.
Fiz. Tverd. Tela (St. Petersburg) 40, 534–536 (March 1998) 相似文献
20.
A series of vanadium-doped lithium niobate (LN:V) crystals has been grown and their photorefractive properties were investigated. For 0.1 mol. % V-doped LiNbO(3), a fast photorefractive response of 160 ms was obtained with a 351 nm laser and a total light intensity of 583 mW/cm(2). The measurements of the x-ray photoelectron spectrum and electron paramagnetic resonance show that V(3+), V(4+), and V(5+) ions exist in these LN:V crystals. V(3+) and V(4+) ions correspond to the 420 and 475 nm absorption peaks, respectively. The fast photorefractive response and high sensitivity indicate that LN:V is a suitable candidate for UV photorefractive applications. 相似文献