Waveguiding behavior of VLS-grown one-dimensional Ga-doped In2O3 nanostructures

Highly crystalline undoped and Ga-doped indium oxide nanorods with square-shaped faceted morphology were fabricated through the vapor-liquid-solid process at moderate temperature. Effects of Ga incorporation on the growth rate, morphology, and crystallinity of the nanostructures were evaluated by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Defect structure and waveguiding behavior of the 1-D In₂O₃ nanostructures have been studied using microRaman and micro photoluminescence spectroscopies. The appearance of several resonant modes superposed over the broad room temperature micro-photoluminescence spectra of the nanostructures demonstrates their waveguiding behaviors. While the pristine or undoped In₂O₃ nanostructures of 20–150 nm widths revealed Fabry-Pérot resonance modes, the Ga-incorporated nanostructures of 20–100 nm width revealed whispering gallery modes due to their smaller widths. The quality factor (Q) of the resonators was estimated to be about 20.86 and 188.79 for the pristine and Ga-incorporated nanostructures, respectively, indicating a huge enhancement due to Ga incorporation. The increment in the Q factor on Ga incorporation in In₂O₃ nanorods opens up the possibility of their utilization for the development of new optical transmitters and resonators, and fabrication of nanoscopic lasing devices.     

Hydrothermal synthesis of 3D Cu0.45Mn0.55O2 nanostructures; lattice vibrations and novel photoluminescence properties

In this paper, Novel 3D Cu_0.45Mn_0.55O₂ nanoarchitectures self-assembled by interconnecting densely stacked nanosheets have been successfully synthesized by facile hydrothermal growth method. The crystalline phase, morphology, particle size and component of the as-prepared nanomaterial were characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy and Raman spectroscopy. FESEM analysis shows that the size of 3D Cu_0.45Mn_0.55O₂ nanostructures is in the range of 1–1.5 μm, and the thickness of interconnected nanosheets is about 45 nm on the average. The structural features of as-synthesized Cu_0.45Mn_0.55O₂ nanostructures are studied to analyze the near-neighbor environment of oxygen coordination around manganese and copper cations reported for the first time using Raman scattering spectroscopy. Moreover, the novel photoluminescence spectra of the as-prepared Cu_0.45Mn_0.55O₂ nanostructures are reported exhibiting prominent emission bands located in red-violet spectral region.     

Shape evolution, photoluminescence and degradation properties of novel Cu2O micro/nanostructures

Three kinds of novel cuprous oxide (Cu₂O) micro/nanostructures are synthesized via a facile template-free hydrothermal method. Two factors are critical for the growth process of typical samples: the concentration of copper ions (Cu(II)) and the addition of Polyvinylpyrrolidone (PVP) as surfactant. It is found that the application of ethanol as solvent speeds up the reduction rate of Cu(II), and it promotes the aggregating of Cu₂O nanocrystals at the preliminary stage to form irregular spherical structures. Photoluminescence (PL) properties of the three kinds of samples and their photocatalytic activities for degradation of Methyl Orange (MO) are also measured. The sample with higher concentration of copper vacancy (V _Cu) defects has better photocatalytic ability, indicating that besides the morphology of Cu₂O nano/microcrystals, the defects in crystalline structures can also influence their electrical characteristics, and thus change their photocatalytic activity. This provides a potential method to improve the photocatalytic performances of Cu₂O crystals.     

Nd3+掺杂B2O3-Nb2O5-BaO-La2O3玻璃光谱性质的研究

 用高温熔融法制备了Nd³⁺(物质的量分数2％）掺杂40B₂O₃-(15-χ)Nb₂O₅-45BaO-χLa₂O₃玻璃，测量了样品的吸收光谱、发射光谱和差热分析（DTA）曲线。根据Nd3+光学跃起矩阵的特点，应用Judd-Ofelt理论，从吸收光谱获得了Nd³⁺光学跃起的强度参数。并计算了Nd³⁺离子的自发辐射跃迁几率、总自发辐射几率、荧光分支比、辐射能级寿命和受激发射截面。结果表明：该体系玻璃中，随着Nb₂O₅ 含量的增加和La₂O₃₂增大，说明材料的对称性降低；而Ω₆减小，说明Nd-O键的共价性和键强增强；受激发射截面减小。DTA实验表明，随着Nb₂O₅含量的增加，材料的热稳定性提高。     

Comparison of optical properties of Cu-Al2O3 and Ag-Al2O3 nano-array composite structure

Cu-Al2O3 (Ag-Al2O3) nano-array composite structures were obtained by alternating current (AC) electrodeposition Cu (Ag) into the pores of anodic alumina.     

Spectroscopic properties of Er3+-doped AlF3-La2O3-Al2O3-SiO2 glasses

Er3+-doped fluoride lanthanum aluminosilicate glasses with compositions of (65- x/2)SiO2 · (25 -and their glass transition temperatures and spectroscopic properties were investigated. The Ω2, Ω4, and Ω6 intensity parameters of glasses were calculated by Judd-Ofelt theory from absorption curves. It was found that glasses transition temperature and melting temperature decreased with the increase of fluoride content in glass, Ω2 decreased gradually with the increase of AlF3 content, but both Ω4 and Ω6 did not increase until AlF3 content increased to 30 mol%. The quantum efficiency of 4I13/2 to 4I15/2 transition of Er3+ ions increases with the increase of AlF3 content in glass. Fluorescent lifetime is longer in glass containing more AlFa content.     

Optical and scintillation properties of Sc2O3, Y2O3 and Lu2O3 transparent ceramics synthesized by SPS method

Sc₂O₃, Y₂O₃ and Lu₂O₃ transparent ceramics were prepared by the spark plasma sintering (SPS) method. After polishing, the samples were semitransparent. Their optical transmittance was 10–40% at 500 nm which corresponded with their semi-transparency. In the X-ray induced emission spectra, a broad emission peak appeared around 335 nm in each sample. For this wavelength, scintillation decay time for Y₂O₃ and Sc₂O₃ were 22 and 48 ns, respectively. The light yield of Sc₂O₃, Y₂O₃ and Lu₂O₃ was 16,200, 2600, and 200 ph/5.5 MeV-alpha, respectively, which followed from the alpha-ray induced pulse height spectra. The gamma-ray induced light yield of Sc₂O₃ was 11,500 ph/MeV, which is 1.4 times larger than that of conventional single crystal BGO (Bi₄Ge₃O₁₂) scintillator. Light yield non-proportionality and energy resolution of Sc₂O₃ were examined for the first time.     

Dielectric properties of Sb2O3 films

A study has been made of the dielectric constant, dielectric loss, electrical conductivity in weak and strong fields, and the dielectric strength of polycrystalline Sb₂O₃ films produced by vacuum evaporation. Electronic polarization is shown to dominate in these films. The nonlinear voltage dependence of the current in strong fields is easily explainable in terms of a Frenkel mechanism for electrostatic ionization. The film breakdown is due to impact ionization of impurities and the formation of a shower.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 5, pp. 52–55, May, 1969.     

Defect properties of Ti-doped Cr2O3

The defects in Cr_2−xTi_xO₃ (x = 0, 0.2 and 0.3) were studied by a combination of X-ray diffraction, density and electrical conductivity measurements supported by atomistic simulation. The results are consistent with the Ti being dissolved as Ti⁴⁺ compensated by Cr vacancies which associate to form complex defects of lower energy. Ti doping gives n-type semiconductivity due to a small concentration of Ti³⁺ in equilibrium with the complexes.     

Plasmonics properties of nano-torus: An FEM method

Nano-torus particles are promising in nano-photonics applications. In this paper, we investigate the plasmonics resonant spectrum of torus and the corresponding horizontal and vertical dimers with the finite element method (FEM) based on strict electromagnetic theory. Compared with sphere, single torus and horizontal dimer under perpendicular polarization are characterized with narrower line width and wider tunability throughout visible and infrared frequencies. These properties make single torus and horizontal dimer suitable for high sensitivity sensing. Furthermore, Purcell factor and local field enhancement of horizontal dimer which are important to high efficient single photon devices are one order of magnitude higher than those of single torus respectively. However, vertical dimer under perpendicular polarization has no above advanced characteristics.     

Photoelectric properties of In2O3-CdSiAs2 structures

Photosensitive rectifying heterostructures were prepared based on single crystals of p-CdSiAs₂ doped with group-III impurities by depositing In₂O₃ layers. It was established that the slope of the long-wave edge of the photosensitivity of the obtained structures decreases as the CdSiAs₂ hole concentration increases. Based on polarization investigations of the photocurrent, a conclusion is drawn concerning the possibilities for practical application of diode structures in polarization photoelectronics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 12–15, April, 1990.     

Structure and ultrafast ethanol sensing properties of In2O3-capped Zn-doped Fe2O3 nanorods

This paper reports the facile synthesis of In₂O₃-capped Zn-doped Fe₂O₃ nanorods along with their ethanol gas sensing properties. A two-stage process involving thermal oxidation of Fe foils and Zn powders in air and the sputter-deposition of In₂O₃ was used to synthesize these nanostructures. The nanorods synthesized using this method were ∼5 μm in length and 50–120 nm in diameter with a shell layer thickness of 10–15 nm. The multiple-networked In₂O₃-capped Zn-doped Fe₂O₃ nanorod sensor showed a significantly enhanced and ultrafast response to ethanol gas. The enhanced sensing performance was explained by modulation of the potential barrier height and the strong catalytic activity of In₂O₃ for ethanol oxidation.     

Magnetic properties of partially devitrified B2O3-MnFe2O4 glass

Crystallization processes of partially devitrifled glass obtained by rapid quenching of 0·17₅ MnO + 0·17₅. Fe₂O₃ + 0·65 B₂O₃ melt were studied by DTA and X-ray analyses and the temperature regions of nucleation, crystallization and decompozition of the spinel phase were established. The magnetization curves measured between 4·2 and 250 K in magnetic fields up to 42 kOe divided the samples into two groups: the original as cast glass and those annealed below the crystallization temperature, as well as above the decomposition temperature showed essentially paramagnetic behaviour, whereas those annealed closely above the crystallization temperature displayed a spontaneous magnetic moment. The former ones could not be classified as superparamagnetic but the temperature dependence of their susceptibility could be explained by interactions of the antiferromagnetic type. The comparison of lattice parameter and Curie temperature of the latter one with crystalline Mn _x Fe_3-x O₄, system indicated pronounced iron enrichment of the spinel phase formed during heat treatment.Based on a paper presented at the Conference of Socialist Countries on Magnetic Oxides and Compounds; Reinhardsbrunn bei Friedrichroda, GDR, October 22nd–27th, 1972.The authors thank Mrs. A.Hadincová for the help with the evaluation of the results.     

Spectroscopic properties of the Pr3+ ion in TeO2-WO3-PbO-La2O3 and TeO2-WO3-PbO-Lu2O3 glasses

The goal of this work was to investigate the spectroscopic properties of Pr³⁺ ions, embedded in two different tellurite glass matrices, TeO₂-WO₃-PbO-La₂O₃ and TeO₂-WO₃-PbO-Lu₂O₃. The absorption and fluorescence spectra have been recorded and analyzed in terms of the Judd-Ofelt theory along with the luminescence decay of the ³P₀ and ¹D₂ levels of the Pr³⁺ ion. The spectroscopic studies were completed with ellipsometric measurements providing the dispersion relation of the refractive index of the investigated glasses.     

一维Ni0.5Zn0.5Fe2O4/SiO2复合纳米结构的制备及其磁性能

采用溶胶-凝胶法结合静电纺丝技术制备了Ni_0.5Zn_0.5Fe₂O₄/SiO₂复合纳米纤维.利用热重-差热分析、X射线衍射、场发射扫描电镜、高分辨透射电镜和振动样品磁强计研究了前驱体纤维的热分解及相转化过程以及焙烧温度和SiO₂含量对目标纳米纤维的相组成、微观结构、形貌及磁性能的影响.结果表明,在450 ℃焙烧时,立方尖晶石结构已基本形成.随着焙烧温度由450 ℃升高到100     

Ga2O3组分对Tm 3+掺杂GeO2-Ga2O3-Li2O-BaO-La2O3玻璃的光谱性能影响

制备了Tm3 (8.0mol%)掺杂(77-x)GeO2-xGa2O3-8Li2O-10BaO-5La2O3(x=4,8,12,16)系列玻璃.系统地研究了Ga2O3从4mol%变化到16mol%时,玻璃的光谱性质与热学性质的变化规律.差热分析表明,随着Ga2O3含量的增加,锗酸盐玻璃的热稳定性增加.运用Judd-Ofelt(J-O)理论计算得到了Tm3 在不同Ga203含量的GeO2-Ga2O3-Li2O-BaO-La2O3玻璃中的J-O强度参数(Ω2,Ω4,Ω6)及Tm3 各激发能级的自发跃迁概率、荧光分支比以及辐射寿命等光谱参量.在808nm激光二极管的激发下,测试并分析了Ga2O3对Tm3 荧光光谱特性的影响.随着Ga2O3从4t001%增加到16mol%,Tm3 在1.8μm处的荧光强度呈现先减弱后增强的特性.当Ga2O3含量大约在12mol%时,Tm3 在1.8μm处的荧光强度最弱,受激发射截面达到最小.还初步讨论了Ga2O3对玻璃结构与光谱参数的影响规律.     

Ferrimagnetic properties of Eu3Ti2O7

The Mossbauer spectrum of ¹⁵¹Eu₃Ti₂O₇ reveals a ferrimagnetic ordering below (8 ± 0.3) K with two inequivalent sites in ratio 2: 1, and with exchange constants nearly equal to those of EuTiO₃ and of Eu₂TiO₄. The sublattice magnetizations are explained in terms of these constants.