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1.
The fluorine-doped tin oxide films (FTO) were prepared with SnCl2 and SnCl4 precursors using the spray pyrolysis method. The vibrational feature of oxygen vacancy in FTIR has been identified. The oxygen vacancy plays a role of donor in FTO films, although it becomes inconspicuous with an increase in fluorine concentration in the solution. The substitution of fluorine for oxygen has also been confirmed by FTIR spectrum, and it further indicates the production of fluorine doping is α-SnF2. The reflectivity shows a close relation with the carrier concentration, suggested by the Drude theory. The discussion of scattering mechanism in FTO films suggests that impurity ions are the main scattering centers for free carriers. 相似文献
2.
3.
B. ChoudhuryA. Choudhury A.K.M. Maidul IslamP. Alagarsamy M. Mukherjee 《Journal of magnetism and magnetic materials》2011,323(5):440-446
Co doped TiO2 nanoparticles have been synthesized by a simple sol-gel route taking 7.5, 9.5 and 10.5 mol% of cobalt concentration. Formation of nanoparticles is confirmed by XRD and TEM. Increase in d-spacing occurs for (0 0 4) and (2 0 0) peak with increase in impurity content. Valence states of Co and its presence in the doped material is confirmed by XPS and EDX. The entire vacuum annealed samples show weak ferromagnetism. Increased magnetization is found for 9.5 mol% but this value again decreases for 10.5 mol% due to antiferromagnetic interactions. A blocking temperature of 37.9 K is obtained, which shows shifting to high temperature as the dopant concentration is increased. The air annealed sample shows only paramagnetic behavior. Temperature dependent magnetic measurements for the air annealed sample shows antiferromagnetic behavior with a Curie-Weiss temperature of −16 K. Here we report that oxygen vacancy and cobalt aggregates are a key factor for inducing ferromagnetism-superparamagnetism in the vacuum annealed sample. Appearance of negative Curie-Weiss temperature reveals the presence of antiferromagnetic Co3O4, which is the oxidation result of metallic Co or cobalt clusters present on the host TiO2. 相似文献
4.
Mohd Rafie JohanOon Hooi Shy Suriani Ibrahim Siti Mariah Mohd YassinTay Yin Hui 《Solid State Ionics》2011,196(1):41-47
A solid polymer electrolyte (SPE) is synthesized by solution casting technique. The SPE uses poly(ethylene oxide) PEO as a host matrix doped with lithium triflate (LiCF3SO3), ethylene carbonate (EC) as plasticizer and nano alumina (Al2O3) as filler. The polymer electrolytes are characterized by Impedance Spectroscopy (IS) to determine the composition of the additive which gives the highest conductivity for each system. At room temperature, the highest conductivity is obtained for the composition PEO-LiCF3SO3-EC-15%Al2O3 with a value of 5.07 10− 4 S/cm. The ionic conductivity of the polymer electrolytes increases with temperature and obeys the Arrhenius law. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) studies indicate that the conductivity increase is due to an increase in amorphous content which enhances the segmental flexibility of polymeric chains and the disordered structure of the electrolyte. Fourier transform infrared spectroscopy (FTIR) spectra show the occurrence of complexation and interaction among the components. Scanning electron microscopy (SEM) images show the changes morphology of solid polymer electrolyte. 相似文献
5.
Oxide ion conductivity of the pure and aliovalent ion substituted rare-earth pyrohafnates in the series RE2−xSrxHf2O7 and RE2Hf2−xAlxO7 (RE=Gd and Nd; x=0–0.2) has been explored in the temperature range 400°C–700°C for the first time. It is seen that, conductivity is enhanced by doping 5 atom% Sr at the rare–earth site in these systems. Well defined impedance plots due to grain interior and grain boundary resistances were obtained in the Gd pyrohafnate with Sr substitution. The results of the conductivity variation for the pure, Sr and Al doped phases are explained on the basis of pyrochlore structure. 相似文献
6.
基于密度泛函理论框架下的第一性原理平面波超软赝势方法,构建了未掺杂与相同重氧空位金红石型和锐钛矿型TiO1.9375超胞模型,分别对模型进行了几何结构优化、能带结构分布和态密度分布的计算. 结果表明,氧空位后金红石型和锐钛矿型TiO2体系体积均变大,同时,锐钛矿型TiO1.9375超胞的稳定性、迁移率以及电导率均高于金红石型TiO1.9375超胞. 计算结果和实验结果相一致.
关键词:
重氧空位
2')" href="#">金红石型和锐钛矿型TiO2
导电性能
第一性原理 相似文献
7.
Effect of lattice strain on the oxygen vacancy formation and hydrogen adsorption at CeO2(111) surface 总被引:1,自引:0,他引:1
Using first-principles calculation, the effect of lattice strain on the oxygen vacancy formation at CeO2(111) surface has been investigated. The tensile strain facilitates the oxygen vacancy formation at the surface and the compressive strain hinders the process. This is in part due to the strengthening or weakening of the surface Ce–O bond under the lattice strain. On the other hand, a more open surface with a larger lattice constant can better accommodate the larger Ce3+ and thus facilitate the structural relaxation of the reduced surface. The studies on the strain effect on the atomic hydrogen adsorption at the defect-free CeO2(111) surface show that the adsorption strength monotonously increases with the increase of the lattice strain, further confirming the tunable surface chemical activity by lattice strain. 相似文献
8.
S. Berger J. Roos A.Yu. Zavidonov D. Brinkmann 《Solid state nuclear magnetic resonance》1998,10(4):197-203
Spin-lattice relaxation studies on the stationary 31P nucleus have been performed in order to investigate to which extent the dynamics of the mobile lithium ions are reflected in the behavior of the glassy network. The temperature dependence of the 31P relaxation, which is governed by the heteronuclear dipole-dipole interaction between lithium and phosphorus, can be described in terms of a Gaussian distribution of activation energies and that over a wide frequency range from about 34 kHz to 81 MHz. A relaxation rate maximum, which provides useful information about correlation times and activation energies of the lithium-ion diffusion process, could only be observed in the rotating frame relaxation measurements. 相似文献
9.
The Rietveld analysis of ND patterns of polycrystalline Li0.2 − xNaxLa0.6TiO3 (0 ≤ x < 0.2) samples, recorded between 300 and 1075 K, shows an orthorhombic–tetragonal transformation, in which the octahedral tilting along the b axis is eliminated at ~ 773 K, but the vacancy ordering along the c axis remains. In Li rich samples, conductivity (10− 3 Ω− 1 cm− 1 at 300 K) departs from the Arrhenius behaviour, decreasing activation energies from 0.37 to 0.14 eV when octahedral tilting is eliminated. Successive Maxwell–Wagner blocking processes, detected in the real part of dielectric constant plots, have been ascribed to the Li blocking at interior domains, grain-boundary and electrode–electrolyte interfaces. The substitution of Li+ by Na+ decreases the amount of vacant A-sites, decreasing several orders of magnitude the conductivity when the amount of vacancies approaches the vacancy percolation threshold (np = 0.27). Below the percolation threshold, Li ions only display local mobility, remaining confined into small domains of perovskites. 相似文献
10.
The stoichiometry range and lithium ion conductivity of Li5+x
Ba
x
La3−x
Ta2O12 (x = 0, 0.25, 0.50, 1.00, 1.25, 1.50, 1.75, 2.00) with garnet-like structure were studied. The powder X-ray diffraction data
of Li5+x
Ba
x
La3−x
Ta2O12 indicated that single phase oxides with garnet-like structure exist over the compositional range 0 ≤ x ≤ 1.25; while for x = 1.5, 1.75 and 2.00, the presence of second phase in addition to the major garnet like phase was observed. The cubic lattice
parameter increases with increasing x and reaches a maximum at x = 1.25 then decreases slightly with further increase in x in Li5+x
Ba
x
La3−x
Ta2O12. The impedance plots of Li5+x
Ba
x
La3−x
Ta2O12 samples obtained at 33 °C indicated a minimum grain-boundary resistance (R
gb) contribution to the total resistance (R
b + R
gb) at x = 1.0. The total (bulk + grain boundary) ionic conductivity increases with increasing lithium and barium content and reaches
a maximum at x = 1.25 and then decreases with further increase in x in Li5+x
Ba
x
La3−x
Ta2O12. Scanning electron microscope investigations revealed that Li6.25Ba1.25La1.75Ta2O12 is much more dense, and the grains are more regular in shape. Among the investigated compounds, Li6.25Ba1.25La1.75Ta2O12 exhibits the highest total (bulk + grain boundary) and bulk ionic conductivity of 5.0 × 10−5 and 7.4 × 10−5 S/cm at 33 °C, respectively. 相似文献
11.
Ensi CaoYongjia Zhang Lin JuLihui Sun Hongwei QinJifan Hu 《Applied Surface Science》2012,258(8):3795-3799
(1 0 0) oriented BaNb2O6 films have been successfully grown on LaAlO3 (1 0 0) substrate at 750 °C or 450 °C in vacuum by pulsed laser deposition. The deposited BaNb2O6 PLD films exhibit room-temperature ferromagnetism. Ab initio calculations demonstrate that stoichiometric BaNb2O6 and that with barium vacancy are nonmagnetic, while oxygen and niobium vacancy can induce magnetism due to the spin-polarization of Nb s electrons and O p electrons respectively. Moreover, ferromagnetic coupling is energetically more favorable when two Nb/O vacancies are located third-nearest-neighbored. The observed room temperature ferromagnetism in BaNb2O6 films should be mainly induced by oxygen vacancies introduced during vacuum deposition, with certain contribution by Nb vacancies. 相似文献
12.
The polymer Lexan was irradiated to 80MeV O6+ ion beam using the 15UD pelletron at Inter University Accelerator Centre, New Delhi. The ion fluence ranging from 1011 to 3 × 1012 ions/cm2 has been used to study the dose effects of irradiation on Lexan. By using the etching technique, it is observed that the
bulk etch rate of the sample increases with increasing the ion influence, while the activation energy associated with it show
a decreasing trend which can be explained on the basis of polymer degradation.
相似文献
13.
Waranyu PipornpongRaina Wanbayor Vithaya Ruangpornvisuti 《Applied Surface Science》2011,257(24):10322-10328
The adsorption energies for physisorption and the most stable chemisorption of CO2 on the neutral charge of perfect anatase [TiO2] (0 0 1) are −9.03 and −24.66 kcal/mol on the spin-unpolarized and −12.98 and −26.19 kcal/mol on the spin-polarized surface. The small activation barriers of 1.67 kcal/mol on the spin-unpolarized surface and of 6.66 kcal/mol on the spin-unpolarized surface were obtained. The adsorption mechanism of CO2 on the oxygen vacancy defect [TiO2 + VO] surface of anatase TiO2 using density functional theory calculations was investigated. The energetically preferred conversion of CO2 to CO was found either on the spin-unpolarized or spin-polarized surfaces of oxygen vacancy defect surface [TiO2 + VO] as photocatalyst. 相似文献
14.
The dependence of Li mobility on structure and composition of Li0.5 − xNaxLa0.5TiO3 perovskites (0 ≤ x ≤ 0.5) has been investigated by means of neutron diffraction, nuclear magnetic resonance and impedance spectroscopy. At 300 K, all samples display a rhombohedral superstructure (R-3c S.G.), where octahedra are out of phase tilted along [111] direction of the ideal cubic cell. The elimination of the octahedral tilting is responsible for the rhombohedral–cubic transformation, detected near 1000 K. In these perovskites, La and Na cations are randomly distributed in A sites, but Li ions are fourfold coordinated at unit cell faces of the cubic perovskite. Lithium conductivity, σ300 K, decreases with the sodium content, decreasing from values typical of fast ionic conductors, 10− 3 S/cm, to those of good insulators, 10− 10 S/cm, when the interconnectivity between vacant A sites is lost (x > 0.3). In samples with x < 0.3, dc conductivity displays a non-Arrhenius behaviour, decreasing activation energy from ~ 0.37 to 0.25 eV when the sample is heated between 77 and 500 K. The temperature dependence of BLi factors shows the existence of two regimes for Li motion. Below 373 K, Li ions remain partially located near square oxygen windows that connect contiguous A sites, but above 400 K, extended Li motions become dominant. The additional decrease of activation energy from 0.25 to 0.16 eV (low-temperature 7Li NMR value), should require the full elimination of octahedral tilting which is only produced above 1000 °C. 相似文献
15.
N. MtiraouiA. Dhahri M. OumezineJ. Dhahri E. Dhahri 《Journal of magnetism and magnetic materials》2011,323(22):2831-2836
The influence of the silver Ag-substitution for Pb ions in the mixed valence perovskites La0.67Pb0.33−xAgxMnO3 (0≤x≤0.15) was investigated by X-ray magnetic and electric transport measurements. All compositions were synthesized using the sol-gel technique. X-ray diffraction and structure refinement show that they crystallize in the rhombohedral structure with the R3?c space group. Upon Ag doping on Pb sites, the lattice parameters, unit cell volume, and the Mn-O-Mn bond angle are reduced. All the samples exhibit a ferromagnetic-paramagnetic transition and metallic-semi-conductor one with increasing temperature. The substitution of Pb by Ag has great influence on the magnetic and electrical transport properties of this family of compounds, decreasing continuously both the Curie temperature (from 361 to 290 K) and the resistivity transition temperature Tp. 相似文献
16.
Rong Li Qiang Zhen Michel DracheAnnick Rubbens Claude EstournesRose-Noëlle Vannier 《Solid State Ionics》2011,198(1):6-15
Using (Bi2O3)0.75(Dy2O3)0.25 nano-powder synthesized by reverse titration co-precipitation method as raw material, dense ceramics were sintered by both Spark Plasma Sintering (SPS) and pressureless sintering. According to the predominance area diagram of Bi-O binary system, the sintering conditions under SPS were optimized. (Bi2O3)0.75(Dy2O3)0.25 ceramics with relative density higher than 95% and an average grain size of 20 nm were sintered in only 10 min up to 500 °C. During the pressureless sintering process, the grain growth behavior of (Bi2O3)0.75(Dy2O3)0.25 followed a parabolic trend, expressed as D2 − D02 = Kt, and the apparent activation energy of grain growth was found to be 284 kJ mol− 1. Dense (Bi2O3)0.75(Dy2O3)0.25 ceramics with different grain sizes were obtained, and the effect of grain size on ion conductivity was investigated by impedance spectroscopy. It was shown that the total ion conductivity was not affected by the grain size down to 100 nm, however lower conductivity was measured for the sample with the smallest grain size (20 nm). But, although only the δ phase was evidenced by X-ray diffraction for this sample, a closer inspection by Raman spectroscopy revealed traces of α-Bi2O3. 相似文献
17.
LaAlO3 crystals have been investigated with differential scanning calorimetry (DSC), high-precision X-ray powder diffraction (XRD) and scanning force microscopy (SFM). The DSC measurements show the second-order phase transition of LaAlO3 at 544°C, where LaAlO3 changes its symmetry from the cubic Pm3m high-temperature phase to the pseudocubic rhombohedral
low-temperature phase. This paraelastic to improper ferroelastic phase transition causes twinning in the {100} and {110} planes of the pseudocubic lattice. The twin angles between the surface {100}pseudocubic planes of twin domains were measured by SFM on the surface of a macroscopic (100)cubic cut crystal plate. The misorientation angle ω100 between {100} twins is 0.195(8)°, while {110} twinning gives an angle of ω110=0.276(7)°. The two twin kink angles correspond to a rhombohedral angle of the pseudocubic cell of the
phase as 1=90.0973(40)° and 2=90.0975(30)°, respectively. The XRD result for this rhombohedral angle is =90.096(1)°. The orientation of the misfit steps formed during annealing after mechanical surface polishing depends on the domain orientation and pattern during polishing. Any heating close to or above Tc changes the domain pattern. Footprints of previous domain patterns can thus be found on the surface in the form of surface corrugation and changes in the shape and orientation of misfit steps. 相似文献
18.
P.J. von Ranke B.P. AlhoE.P. Nóbrega V.S.R. de SousaT.S.T. Alvarenga A. Magnus G. CarvalhoN.A. de Oliveira 《Journal of magnetism and magnetic materials》2012,324(7):1290-1295
We report on the magnetic and magnetocaloric effect calculations in antiferromagnetic perovskite-type EuTiO3. From the isothermal magnetic entropy change calculated upon low magnetic field changes (below 1 T) several results were predicted: inverse magnetocaloric effect, latent heat associated to spin AFM-FM reorientation transition and a temperature interval (controlled by magnetic field) where the EuTiO3 does not change heat in an isothermic process. The magnetocaloric effect described through magnetic entropy change was correlated with magnetocapacitance formula. The theoretical investigation was carried out using a Heisenberg Hamiltonian considering the G-type antiferromagnetic structure with exchange interactions, in mean field approximation, between nearest-neighbor and next-nearest-neighbor magnetic Eu+2 ions. 相似文献
19.
Cu0.62Zn0.38 brass foils were thermally oxidized at 500 °C under various gaseous environments, including nitrogen, air and mixture of N2–O2 at a pressure of 1 atm for 3 h. The oxidized specimens were characterized with a scanning electron microscope, an X-ray diffractometer and a transmission electron microscope. Optical property of oxidized products was characterized by photoluminescence. It is found that the nanowires and/or nanowalls are formed from hexagon ZnO crystals under N2–O2 gases and air. However, nanowires and nanowalls cannot form on the specimens oxidized in N2. When oxygen partial pressure of environment is over a critical value, increasing oxygen partial pressure is of disbenefit to the growth of nanowires and nanowalls and reduces the thickness of oxide scale on a specimen. The experimental results are explained by the defect equilibrium theory of oxide scale and the compressive growth stresses occurred during oxidation. 相似文献
20.
X. M. Xiong Z. Q. Peng Y. L. Zhou Z. H. Cheng H. B. Lu H. S. Wang D. F. Cui L. Li G. Z. Yang 《Physica C: Superconductivity and its Applications》1997,280(4):266-268
Our investigation on the relation between oxygen content and the laser-induced voltages of the YBa2Cu3O7−δ films in normal-state shows that deoxygenation of the superconducting films reduces the laser-induced voltages greatly, even reverses the sign of the signals at large oxygen deficiency. The absolute value of the negative signal at large oxygen deficiency can be greater than that of the positive signal. 相似文献