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31.
Jiong Zhao Honggi Nam Thuc Hue Ly Seok Joon Yun Sera Kim Suyeon Cho Heejun Yang Young Hee Lee 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(1)
Defects in bulk crystals can be classified into vacancies, interstitials, grain boundaries, stacking faults, dislocations, and so forth. In particular, the vacancy in semiconductors is a primary defect that governs electrical transport. Concentration of vacancies depends mainly on the growth conditions. Individual vacancies instead of aggregated vacancies are usually energetically more favorable at room temperature because of the entropy contribution. This phenomenon is not guaranteed in van der Waals 2D materials due to the reduced dimensionality (reduced entropy). Here, it is reported that the 1D connected/aggregated vacancies are energetically stable at room temperature. Transmission electron microscopy observations demonstrate the preferential alignment direction of the vacancy chains varies in different 2D crystals: MoS2 and WS2 prefer direction, while MoTe2 prefers direction. This difference is mainly caused by the different strain effect near the chalcogen vacancies. Black phosphorous also exhibits directional double‐chain vacancies along 〈01〉 direction. Density functional theory calculations predict that the chain vacancies act as extended gap (conductive) states. The observation of the chain vacancies in 2D crystals directly explains the origin of n‐type behavior in MoTe2 devices in recent experiments and offers new opportunities for electronic structure engineering with various 2D materials. 相似文献
32.
33.
为了探讨作为固体氧化物燃料电池电解质材料的可行性,采用交流阻抗谱研究了(Gd2O3)x(ZrO2)1-x(x=0.05-0.15)固体电解质材料的晶粒电导率,并通过分子动力学方法模拟了Gd2O3掺杂ZrO2固体电解质材料的动力学行为,计算并分析了温度和Gd2O3掺杂量对体系离子传导性能的影响.实验和模拟结果均表明,升高温度能明显增强离子电导性能.当Gd2O3掺杂量为8 mol%时,材料的电导性能取得最优值. 相似文献
34.
李华 《南京工业职业技术学院学报》2003,3(4):56-58
本从化与翻译的关系出发,论述了英汉互译中由于化差异造成的词汇空缺现象五方面的表现,并由归化、异化入手探讨了化解的方法。 相似文献
35.
The Raman and X-ray photoemission spectroscopy of lanthanum-doped SrBi4Ti4O15 (SBLT -x, x =0.00, 0. 05, 0. 10, 0. 25, 0.50, 0. 75 and 1.00) ferroelectric ceramics were investigated to explore the La substitution site and the influence of La-doping on the oxygen vacancy concentration. The results suggest that La3 ions behave pronounced site selectivity for the A site in the case of x ≤ 0.10, and they are incorporated into Bi2O2 layers at higher content. The oxygen vacancy concentration declines with La-doping, and the decrease seems saturated as La content is higher than 0.10. 相似文献
36.
《Ceramics International》2017,43(2):1997-2003
The single-phase Ni-doped PbPdO2 films with a body-centered orthorhombic structure were synthesized by the sol-gel spin-coating method and an oxidation treatment. The films with a thickness of about 440 nm were found to have a nanograin structure and large amount of Pb vacancies. The valence states of Ni and Pd ions within the Ni-doped PbPdO2 films were very close to 2+, while the Pb ions exhibited a mixed valence between 2+ and 4+. The existence of Pb vacancies and the low electronegativity of Pb2+ ion resulted in the increase of the valence of Pb ions. The analysis of the magnetic properties indicated that the magnetisms of the single-phase Ni-doped PbPdO2 nanograin films were all composed of the ferromagnetism and the paramagnetism. The ferromagnetism enhanced with the calcination temperature increasing and could be retained up to 380 K. A carrier-mediated mechanism bridged to the bound magnetic polaron model based on the Pb vacancies, the doped Ni ions and the Pb ions with a valence higher than 2+ were used to explain the magnetic origin of these Ni-doped PbPdO2 nanograin films. 相似文献
37.
Yangsen Xu Xi Xu Ning Cao Xianfen Wang Xuehua Liu Marco Fronzi Lei Bi 《International Journal of Hydrogen Energy》2021,46(17):10293-10302
The electrochemical conversion of N2 to NH3 is an interesting research topic as it provided an alternative and energy-saving method compared with the traditional way of NH3 production. Although different materials have been proposed for N2 reduction, the use of defects in oxides was only reported recently and the relevant working mechanism was not fully revealed. In this study, Sr was used as the dopant for LaFeO3 to create oxygen vacancies, forming the Sr-doped LFO (La0.5Sr0.5FeO3-δ) perovskite oxide. The La0.5Sr0.5FeO3-δ ceramic oxide used as a catalyst achieves an NH3 yield of 11.51 μgh?1 mg?1 and the desirable faradic efficiency (F.E.) of 0.54% at ?0.6 V vs reversible hydrogen electrode (RHE), which surpassed that of LaFeO3 nanoparticles. The 15N isotope labeling method was employed to prove the La0.5Sr0.5FeO3-δ catalyst had the function of converting N2 into NH3 under the electrolysis condition. The first principle calculations were used to investigate the mechanism at the atomistic level, revealing that the free energy barriers changed significantly with the introduction of oxygen vacancies that accelerated the overall nitrogen reduction reaction (NRR) procedure. 相似文献
38.
Xinchun Xie Tianzi Wang Zhiyong Zhou Guofeng Cheng Ruihong Liang Xianlin Dong 《Journal of the European Ceramic Society》2019,39(4):957-962
Bi4Ti3O12 (BIT), a typical Aurivillius ceramics with high Curie temperature (Tc ? 675 °C), has great potential for high temperature applications. This work provides an effective method of inducing structure distortion, relieving the tetragonal strain of the TiO6 octahedron and decreasing the concentration of oxygen vacancies to improve the piezoelectricity and temperature stability of BIT ceramics. Bi4Ti2.98W0.01Nb0.01O12 possesses an optimum piezoelectric coefficient (d33) of 32 pC/N, a high Tc of 655 °C and a large resistivity of 3 × 106 Ω·cm at 500 °C. The maximum d33 reported here is approximately quadruple than that of pure BIT (?7 pC/N). Moreover, the d33 of W/Nb co-doped BIT and the in-situ temperature stability of the compression-mode sensor present a highly stable characteristic in the range of 25–600 °C. These results imply that W/Nb-modified BIT ceramics is a promising candidate for application at high temperatures of up to 600 °C. 相似文献
39.
Yanfeng Li Denghui Ji Shaopeng Liu Guide Tang Zhuangzhi Li Yuxi Yao Denglu Hou Minggang Zhu 《稀有金属(英文版)》2012,31(4):379-386
The fact that there are Mn2+ at the A sites in the ABO3 perovskite phase of manganites with the nominal composition La0.6-xNdxSr0.1MnO3 showed by detailed experimental study and theoretical calculations.The magnetic moments of these Mn2+ are antiparallel to those of the Mn ions at the B sites.The content of the Mn2+ increases as the average ionic radius,(rA),of the ions at A sites decreases,resulting in the experimentally observed phenomenon that the content of the Mn3O4 phase in the manganites decreases with decreasing 〈rA〉. 相似文献
40.
Enhanced photocatalytic hydrogen production of noble-metal free Ni-doped Zn(O,S) in ethanol solution
Noto Susanto Gultom Hairus Abdullah Dong-Hau Kuo 《International Journal of Hydrogen Energy》2017,42(41):25891-25902
High efficient hydrogen evolved Ni-doped Zn(O,S) photocatalyst with different Ni amounts had been successfully synthesized with a simple method at low temperature. Our Ni-doped Zn(O,S) catalyst reached the highest hydrogen generation rate of 14,800 μmol g?1 h?1 or 0.92 mmol g?1 h?1 W?1 corresponding to apparent quantum yield 31.5%, which was 2.3 times higher compared to the TiO2/Pt used as a control in this work. It was found that a small amount of Ni doped into Zn(O,S) nanoparticles could increase the optical absorbance, lower the charge transfer resistance, accordingly decrease the electron-hole recombination rate, and significantly enhance the photocatalytic hydrogen evolution reaction (HER). The as-prepared catalyst has the characteristics of low cost, low power consumption for activating the catalytic HER, abundant and environmental friendly constituents, and low surface oxygen bonding for forming oxygen vacancies. The photocatalytic performance of Ni-doped Zn(O,S) was demonstrated with a proposed kinetic mechanism in this paper. 相似文献