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1.
Co-doped SnO2 films codoped with nitrogen (N) have been prepared by magnetron sputtering to investigate the effect of p-type defects on magnetic properties. The incorporation of N modifies the preferential growth orientation of the films. Multiple characterization techniques reveal that the incorporated Co2+ and N3− ions substitute for Sn4+ and O2− sites in SnO2 lattice, respectively. As N concentration increases, the band gap of the films decreases because of the formation of Sn-N bond. Room-temperature ferromagnetism is observed in (Co, N)-codoped SnO2 films, and the saturated magnetic moment is sensitive to the incorporated N concentration. The variations in the magnetic properties as a function of N concentration are discussed on the basis of bound magnetic polaron model. 相似文献
2.
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
3.
Luyan Li Yahui Cheng Weihua Wang Shiwei Ren Yitong Yang Xiaoguang Luo Hui Liu 《Solid State Communications》2011,151(21):1583-1587
The ferromagnetic properties of Mn- and Co-doped Cu2O with copper and oxygen vacancies (VCu and VO) are studied by first-principles calculations. The results indicate that Mn-doped Cu2O has an antiferromagnetic state in the near configuration, while it has a ferromagnetic state for the far configuration. On the contrary, Co-doped Cu2O possess a ferromagnetic state regardless of the distance between the two Co atoms. The observed ferromagnetism can be attributed to the 90° ferromagnetic super-exchange mechanism. The presence of VO can enhance the ferromagnetism, whereas VCudepresses it. 相似文献
4.
A novel room temperature solid-state chemical synthesis was introduced to successfully fabricate CeO2 samples, coupled by a polyethylene glycol 400 (PEG 400)/cetyl trimethylammonium bromide (CTAB)/sodium dodecyl sulfate (SDS). The as-prepared products were characterized by XRD, TEM, SEM, BET and UV. A study of photocatalytic degradation of the methylene blue MB under UV illumination has been carried out. It is indicated that the samples exhibit excellent photocatalytic activity. Besides, the samples assisted with surfactants possess higher photocatalytic activity than the sample without any surfactants, wherein the sample with SDS as an additive shows the highest photocatalytic activity, which is able to reach 89.6% MB degradation ratio within 60 min illumination. Moreover, the effects of important operational parameters such as initial MB concentration, catalyst loading and pH were also investigated. The above sample under the optimum conditions obtained the maximum MB degradation ratio up to 96.5%, which is higher than that of the commercial TiO2 P25 under the same conditions. It can be concluded that CeO2 will be a potential photocatalyst in the application of organic pollutant. 相似文献
5.
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
6.
The influence of oxygen vacancy on the magnetism of Co-doped ZnO has been investigated by the first-principles calculations.It is suggested that oxygen vacancy and its location play crucial roles on the magnetic properties of Co-doped ZnO.The exchange coupling mechanism should account for the magnetism in Co-doped ZnO with oxygen vacancy and the oxygen vacancy is likely to be close to the Co atom.The oxygen vacancy (doping electrons) might be available for carrier mediation but is localized with a certain length and can strengthen the ferromagnetic exchange interaction between Co atoms. 相似文献
7.
The surface properties and the activities in catalytic wet air oxidation over CeO2-TiO2 catalysts 总被引:1,自引:0,他引:1
Shaoxia Yang Wanpeng Zhu Zhanpeng Jiang Zhengxiong Chen Jiangbing Wang 《Applied Surface Science》2006,252(24):8499-8505
No-noble metal CeO2-TiO2 catalysts prepared by sol-gel method were developed and examined for catalytic wet air oxidation (CWAO) of acetic acid. The structure of the catalysts was measured by BET, SEM, XRD, XPS and DTA-TG. We investigated the effect of the interactions of Ce and Ti on the structure of CeO2-TiO2 catalysts. The mechanisms of the relationships between the different content of Ti and the activity of CeO2-TiO2 catalysts were discussed. The results showed that the average crystal size of CeO2 decreased and the surface areas increased; the low valence of Ce3+ increase, and the chemisorbed oxygen slightly decreased with the increase of Ti content on the surface of CeO2-TiO2 catalysts. The order of the activity in CWAO of acetic acid followed: Ce/Ti 1/1 > Ce/Ti 3/1 > Ce/Ti 1/3 > Ce/Ti 5/1 > CeO2 > TiO2 > no catalyst. In CWAO of acetic acid, the optimal atomic ratio of Ce and Ti was 1, and the highest COD removal was over 64% at 230 °C, 5 MPa and 180 min reaction time over Ce/Ti 1/1 catalyst. The excellent activity and stability of CeO2-TiO2 catalysts was observed in our study. 相似文献
8.
The effects of humidified atmosphere on oxygen surface exchange and diffusion in La2Mo2O9 have been investigated. After annealing samples in D2O vapour, the depth and line scan profiles of the OD- species showed the incorporation of hydroxyl groups on the surface and of diffusion into the bulk. The hydroxyl diffusion process appears to be different from that of oxygen diffusion, and might indicate the existence of ambipolar diffusion of oxide ions and hydroxyl species in La2Mo2O9. 相似文献
9.
Oxygen vacancy (Ov) has significant influence on physical and chemical properties of TiO2 systems,especially on surface catalytic processes.In this work,we investigate the effects of O v on the adsorption of formaldehyde (HCHO) on TiO2(110) surfaces through firstprinciples calculations.With the existence of Ov,we find the spatial distribution of surface excess charge can change the relative stability of various adsorption configurations.In this case,the bidentate adsorption at five-coordinated Ti (Ti5c) can be less stable than the monodentate adsorption.And HCHO adsorbed in Ov becomes the most stable structure.These results are in good agreement with experimental observations,which reconcile the long-standing deviation between the theoretical prediction and experimental results.This work brings insights into how the excess charge affects the molecule adsorption on metal oxide surface. 相似文献
10.
Jun Fang 《Applied Surface Science》2007,253(22):8952-8961
We have investigated the geometric and electronic structures of the cerium oxide (CeO2)-titanium dioxide (TiO2) mixed oxides with various Ce/TiO2 weight ratios prepared by the sol-gel method in detail by means of X-ray diffraction (XRD), high-resolution X-ray photoelectron spectroscopy (XPS), Raman spectroscopy excited by 325 and 514.5 nm lasers, and scanning electron microscope (SEM). Existence of cerium effectively inhibits the phase transition of TiO2 from the anatase phase to the rutile phase. XRD peaks of TiO2 anatase attenuate continuously with the increasing amount of CeO2 in the mixed oxide, but the XRD peaks of cubic CeO2 appear only after the weight ratio of Ce/TiO2 reaches 0.50. The average crystalline sizes of TiO2 anatase and cubic CeO2 in CeO2-TiO2 mixed oxides are smaller than those in the corresponding individual TiO2 anatase and cubic CeO2. Raman spectroscopy excited by the 514.5 nm laser detects CeO2 after the weight ratio of Ce/TiO2 reaches 0.70 whereas Raman spectroscopy excited by the 325 nm laser detects CeO2 after the weight ratio of Ce/TiO2 reaches 0.90. XPS results demonstrate that Ti exists in the form of Ti4+ in the CeO2-TiO2 mixed oxide. Ce is completely in the form of Ce3+ in the mixed oxides with a 0.05 weight ratio of Ce/TiO2. With the increasing weight ratio of Ce/TiO2, Ce4+ dominates. On basis of these results, we proposed that CeO2 initially nucleates at the defects (oxygen vacancies) within TiO2 anatase, forming an interface bridged with oxygen between CeO2 and TiO2 anatase. At the interface, Ce species cannot substitute Ti4+ in the lattice of TiO2 anatase whereas Ti4+ can substitute Ce4+ in the lattice of cubic CeO2. The decreasing concentration of oxygen vacancies, the Ti-O-Ce interface, and the decreasing average crystalline size of TiO2 anatase act to inhibit the phase transformation of TiO2 anatase. With the increasing amounts of CeO2, the CeO2 clusters continuously grow and form cubic CeO2 nanocrystals. Spectroscopic results strongly demonstrate that the surface region of CeO2-TiO2 mixed oxide is enriched with TiO2. 相似文献
11.
Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition (PLD) under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel (SS) tapes coated by IBAD-YSZ (IBAD-YSZ/SS), and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density (Jc) of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50 nm. The surface morphologies of the two groups of samples are examined by SEM. 相似文献
12.
M. ElMassalami D. da S. OliveiraH. Takeya 《Journal of magnetism and magnetic materials》2011,323(16):2133-2136
Based on extensive Mossbauer effect (ME) and magnetization measurements, the orthorhombic AlFe2B2 was characterized as a ferromagnet (FM) because this character is evident as an onset of a FM transition at Tc=320 K and characteristic magnetizations isotherms below Tc. At liquid helium temperatures, the magnetization saturates to μsat≈1μB per Fe atom; a value which is half the one reported for the iron metal indicating a relatively more filled 3d band. The ME analysis revealed a hyperfine field H(0) of 88(2) kOe, an isomer shift (relative to Fe) of 0.50(2) mm/s, and a quadrupole parameter of 0.02 mm/s: all parameters extrapolated to zero Kelvin. The itinerant character of the magnetic moment will be discussed. 相似文献
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14.
在Si-Al2O3复合薄膜中观察到室温铁磁性.Si的体积百分比为15 %的Si-Al2O3复合薄膜的磁性最强.Si的含量影响样品的磁有序,在样品中观察到了明显的磁畴.在不同气氛下,对样品进行快速热退火.退火样品的磁性测试结果的差别表明氧空位不是样品铁磁性的主要来源.我们认为铁磁性来源于Si与Al2O3基质界面之间的缺陷的磁耦合.改变Si的含量可以改变缺陷密度,从而控制铁磁耦合强度.
关键词:
2O3薄膜')" href="#">Al2O3薄膜
室温铁磁性
掺杂
交换相互作用 相似文献
15.
Several oxides doped with transition metals can be used in spintronics devices due to their conductive and magnetic properties at room temperature. In this work, samples of Ce1−2xZnxCoxO2−δ were obtained by an alternative sol–gel proteic process for x=0.01, 0.05 and 0.1. The structural properties of samples were analyzed by XRD and Raman spectroscopy. Magnetization measurements revealed a ferromagnetic behavior at room temperature probably induced by oxygen vacancies. 相似文献
16.
The structures of LiTiPO5 and LiTi2(PO4)3, as well as the possibility of oxygen vacancies formation in the systems are studied by first-principles calculations. It is found that oxygen vacancies can be formed in LiTiPO5 and LiTi2(PO4)3 under oxygen poor condition. The formation of oxygen vacancies introduce a defect band within their band gaps, which is expected to improve the electronic conductivity of LiTiPO5 and LiTi2(PO4)3 significantly. Meanwhile, a great concentration of oxygen vacancies may increase the discharge voltage of LiTiPO5 and LiTi2(PO4)3. 相似文献
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18.
采用反应磁控溅射方法,在(0001)蓝宝石单晶衬底上,制备了纳米多晶Gd2O3掺杂CeO2(GDC)氧离子导体电解质薄膜,采用X射线衍射仪(XRD)、原子力显微镜(AFM)对薄膜物相、结构、粗糙度、表面形貌等生长特性进行了表征,利用交流阻抗谱仪测试了GDC薄膜不同温度下的电学性能;实验结果表明,GDC薄膜为面心立方结构,在所研究的衬底温度范围内,均呈强(111)织构生长;薄膜表面形貌随衬底温度发生阶段性变化:衬底温度由室温升高到300℃时,
关键词:
2O3掺杂CeO2电解质薄膜')" href="#">Gd2O3掺杂CeO2电解质薄膜
反应磁控溅射
生长特性
电学性能 相似文献
19.
Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti3+-V O defect complexes(or clusters) have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments. 相似文献
20.
W.H. Zhang L. ChenY.T. Tao W.H. ZhangJ. Chen J.X. Zhang 《Physica B: Condensed Matter》2011,406(24):4630-4633
Barium titanate (BaTiO3) crystal samples with different distribution of oxygen vacancies were prepared through different thermal treatment processes. The influences of oxygen vacancies on the Raman spectra and X-ray photoelectron spectroscopy (XPS) spectra of BaTiO3 single crystals were studied comparatively. Raman measurements of fast-cooled BaTiO3, which annealed in vacuum and then cooled in air showed many different spectroscopic results comparing with as-received BaTiO3 sample. Raman measurements of slow-cooled BaTiO3, which annealed in vacuum and then cooled in tube furnace exhibited few spectroscopic differences. XPS measurements of as-received BaTiO3 sample and fast-cooled BaTiO3 sample confirmed that this discrepancy resulted from the surface phase of oxygen vacancy in BaTiO3. 相似文献