Bi2O3—Sb2O3二元系的研究

本文用 X 射线衍射及差热-热重分析方法研究了 Bi_2O_3-Sb_2O_3二元系在 N_2和空气中的相关系.研究结果表明,在 N_2中发生自氧化-还原化学反应5Bi_2O_3+3Sb_2O_3→4Bi+6BiSbO4在空气中 Bi 和 Sb 分别主要以+3和+5价的形式存在.Sb 在 Bi_2O_3中的溶解度不超过3mol%.形成三种化合物:Bi3SbO_7、Bi_5Sb_2O_(12.5)和 BiSbO_4.前两者为包品反应产物,后者为固液同份化合物.BiSbO_4的熔点为1276℃.BiSbO_4与Sb_2O_4属共晶反应.并讨论了Sb 对 Bi-Sr-Ca-Cu-O 体系形成超导相的影响.     

Surface structure of γ-Fe2O3(111)

The surface structure of γ-Fe₂O₃(111) has been investigated with a range of surface techniques. Two different surface structures were discovered depending upon surface preparation techniques. Sputtering followed by annealing in vacuum produced a reduced surface characterised by a (2 × 2) LEED pattern, whereas sputtering followed by annealing in 1 × 10^? 6 mbar oxygen produced a surface characterised by a (√3 × √3)-R30° LEED pattern. The latter appears to be a very low conductivity surface, whereas the former has the band gap expected for maghemite (~ 2.0 eV). We propose that the reduced surface is a magnetite-like layer, whereas the oxidised surface is an Fe₂O₃-like layer.     

Synthesis and characterization of magnetic diphase ZnFe(2)O(4) /γ-Fe(2)O(3) electrospun fibers

Magnetic nanofibers of ZnFe₂O₄/γ-Fe₂O₃ composite were synthesized by electrospinning from a sol-gel solution containing a molar ratio (Fe/Zn) of 3. The effects of the calcination temperature on phase composition, particle size and magnetic properties have been investigated. Zinc ferrite fibers were obtained by calcinating the electrospun fibers in air from 300 to 800 °C and characterized by thermogravimetric analyses, Fourier transformed infrared spectroscopy, X-ray photoemission spectroscopy, X-ray diffraction, vibration sample magnetometry and magnetic force microscopy. The resulting fibers, with diameters ranging from 90 to 150 nm, were ferrimagnetic with high saturation magnetization as compared to bulk. An increase in the calcination temperature resulted in an increase in particle size and saturation magnetization. The observed increase in saturation magnetization was most likely due to the formation and growth of ZnFe₂O₄/γ-Fe₂O₃ diphase crystals. The highest saturation magnetization (45 emu/g) was obtained for fibers calcined at 800 °C.     

Induced crystallization and the physical properties of PbO–Sb2O3–As2O3: MoO3 glass system

PbO–Sb₂O₃–As₂O₃ glasses mixed with different concentrations of MoO₃ (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. The X-ray diffraction and the scanning electron microscopic studies have revealed the presence of Pb₅Sb₂O₈, PbSb₂O₆, SbAsO₄, Sb₂MoO₆, Sb₄Mo₁₀O₃₁, As₄Mo₃O₁₅, Pb₅Sb₄O₁₁ crystalline phases in these samples. The differential thermal analysis indicated that the surface crystallization prevails over the bulk crystallization as the concentration of the crystallizing agent is increased. The infrared (IR) spectral studies exhibit bands due to MoO₄ structural units in addition to the conventional bands due to various antimonate and arsenate structural groups. The studies on PbO–Sb₂O₃–As₂O₃: MoO₃ glass-ceramics with respect to various physical properties viz., dielectric properties over a range of frequency and temperature, optical absorption, electron spin resonance (ESR) and magnetic susceptibility at room temperature have also been reported. The optical absorption, ESR and magnetic susceptibility studies indicated that the molybdenum ions exist in Mo⁵⁺ state in addition to Mo⁶⁺ state in these samples. The redox ratio found to increase as the concentration of the MoO₃ is increased. The variations observed in all these properties with the concentration of the crystallizing agent have been analyzed in the light of different oxidation states and environment of molybdenum ions in the glass ceramic network.     

Synthesis and characterization of (Bi2O3)1−x−y−z(Gd2O3)x (Sm2O3)y(Eu2O3)z quaternary solid solutions for solid oxide fuel cell

Sm₂O₃, Gd₂O₃, Eu₂O₃ triple-doped Bi₂O₃ based quaternary solid solutions were synthesized as a candidate electrolyte material using the solid-state reaction technique. The structural, thermal and electrical conductivity features of the ceramic samples were examined and compared by using X-ray powder diffraction (XRD), thermal gravimetry/differantial thermal analysis (TG/DTA) and the four-point probe technique (4PPT). The result of XRD measurements indicated that the (Bi₂O₃)_{(1−x−y−z)}(Gd₂O₃)_x(Sm₂O₃)_y(Eu₂O₃)_z (x = 10/y = 10/z = 5, 15, 20 mol % and x = 10/y = 5, 10, 15, 20/z = 10 mol %) samples have a stable face-centered cubic δ-phase and mixed phase crystallographic structure. The phase stability was also checked by the DTA evaluations results. The temperature dependent electrical conductivity measurements showed that the highest electrical conductivity was observed for the sample of the (Bi₂O₃)_0.75(Gd₂O₃)_0.10(Sm₂O₃)_0.05(Eu₂O₃)_0.10 system which has a stable and δ-phase was found as 6.67 × 10⁻³ (Ω cm)⁻¹ at 650 °C. This sample can be used as an electrolyte material in the solid oxide fuel cells (SOFCs) which is possible to operate at intermediate temperature ranges. The activation energy was also calculated at a low temperature range (350–650 °C) and high temperature range (above 650 °C). The values for the samples vary from 0.63 eV to 1.08 eV at low temperature and at high temperature they vary from 0.43 eV to 0.75 eV.     

Neutron diffraction study of the oxide conducting δ1-phase of (Bi2O3)1−x(Y2O3)x (x=0.25)

The atomic parameters of the average cell of δ¹-Bi(Y)O_1.5 were determined by powder neutron diffraction. The evidence indicates that the disorder in the structure has many features in common with the structure of the oxygen deficient zirconia. Most oxygens (78%) are in sites displaced 0.335 Å along 〈100〉 directions from the normal fluorite positions, while a smaller proportion (22%) are displaced 0.80 Å along 〈111〉 directions and no oxygen remains in normal positions. In addition to the anion displacements a smaller displacement (0.25 Å) along the 〈111〉 direction was found for the cations. Comparison with the structure of β-Bi₂O₃ suggests that the displacements may be precursors to a δ→β phase transition.     

Electron paramagnetic resonance of quasi-one-dimensional crystal [Nd2(Cl3COO)6(H2O)3]n · nH2O

A quasi-one-dimensional single crystal of [Nd₂(Cl₃COO)₆(H₂O)₃]_n · nH₂O in which chains are built up of two alternating neodymium-ion dimer fragments is studied by the EPR technique. It is found that anisotropic interactions between neodymium ions in a chain are responsible for the complex shape of the EPR spectrum. Two groups of EPR signals are distinguished in the spectrum. Each group corresponds to one of the chain dimers disturbed by the interaction with neighbors in the chain. The shape of the EPR spectra is interpreted as a superposition of the spectra of chain fragments which have different lengths and are formed by the alternating magnetic triplet and nonmagnetic singlet states in the chain. Consideration is given to two cases when two alternating dimer fragments are either equivalent or nonequivalent to each other. It is shown that the spectral shape is primarily determined by the superposition of the spectra of an isolated triplet state (S=1), two interacting triplet states, and three interacting triplet states whose weighting contributions differ for the above two cases. The tensors of the anisotropic spin-spin interaction are determined, and the contribution from the isotropic component of the interaction is estimated.     

Pulsed laser deposition of Eu:Y2O3 thin films on (0001) α-Al2O3

This paper focuses on the preparation and characterization of crystalline thin films of rare-earth-doped sesquioxides (Y₂O₃, Lu₂O₃) grown by pulsed laser deposition on single-crystal (0001) sapphire substrates. X-ray diffraction measurements show that the films with thicknesses between 1 nm and 500 nm were highly textured along the 111 direction. Using Rutherford backscattering analysis, the correct stoichiometric composition of the films was established. The emission and excitation spectra of europium-doped films with a thickness 100 nm look similar to those of the corresponding crystalline bulk material, whereas films with a thickness 20 nm show a completely different emission behavior. PACS 68.55.Jk; 78.66.Nk; 81.15.F     

[Fe3O(Ala)6(H2O)3](ClO4)7和[Fe3O(Gly)6(H2O3)(NO3)7)·3H2O]顺磁共振谱及变温磁化率研究

本文通过对[Fe 3O(Ala) 6(H 2O) 3](ClO 4) 7和[Fe 3O(Gly) 6(H 2O) 3](NO 3) 7·3H 2O的ESR谱的解析及变温磁化率的研究,得出它们的ESR谱具有各向同性的特点;朗德因子分别为2.019和1.997;两种配合物中铁离子间有反铁磁相互作用.     

Optimization of synthesis conditions and composition of blue phosphors [(B2O3)0.5(Al2O3)0.5] · 2SiO2: Eu2+

It is found that [(B₂O₃)_0.5(Al₂O₃)_0.5] · 2SiO₂: Eu²⁺ systems with different concentrations of europium exhibit intense photoluminescence in the blue-violet range. When the system is excited by a 325-nm helium-cadmium laser, the spectra of blue phosphors exhibit a maximum in the interval 419–439 nm, while excitation by a pulsed nitrogen laser with a wavelength of 337 nm causes luminescence between 429 and 461 nm. Phosphor with the composition [(B₂O₃)_0.5(Al₂O₃)_0.5] · 2SiO₂: Eu (3 mol %) (x = 0.151, y = 0.062) excited by the radiation of a helium-cadmium laser and phosphor of the same composition having been subjected to additional vacuum annealing and excited by the radiation of a nitrogen laser (x = 0.145, y = 0.084) are found to be optimal to provide primary blue color in the EBU and NTSC TV standards. Phosphors of the composition [(B₂O₃)_0.5(Al₂O₃)_0.5] · 2SiO₂: Eu²⁺ (7 mol %) offer the highest luminescence intensity both before and after vacuum annealing.     

Valence electronic structure of uranyl nitrate UO2(NO3)2·2H2O

Experimental and theoretical studies on the electronic structure of a uranyl nitrate hydrate, UO₂(NO₃)₂·2H₂O, have been performed by X-ray photoelectron spectroscopy (XPS) and with relativistic DV-Xα molecular orbital methods. The XPS spectra are measured within five minutes of X-ray irradiation, which causes negligible damage to the sample. Taking into consideration the calculated results, each peak of the experimental spectrum is assigned. The theoretical spectrum of the uranyl nitrate is in good agreement with the present experimental spectrum.     

[Fe_3O(Ala)_6(H_2O)_3](ClO_4)_7和[Fe_3O(Gly)_6(H_2O)_3](NO_3)7·3H_2O的顺磁共振谱及变温磁化率研究

本文通过对 [Fe3 O(Ala) 6(H2 O) 3 ](Cl O4) 7和 [Fe3 O(Gly) 6(H2 O) 3 ](NO3 ) 7· 3H2 O的 ESR谱的解析及变温磁化率的研究 ,得出它们的 ESR谱具有各向同性的特点 ;朗德因子分别为 2 .0 19和 1.997;两种配合物中铁离子间有反铁磁相互作用     

Ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramics under compressive stress

Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1−x)Pb(Zr_1/2Ti_1/2)O₃–xPb(Zn_1/3Nb_2/3)O₃ or (1−x)PZT–(x)PZN (x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (P_sat), the remnant polarization (P_r), and the coercive field (E_c) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes.     

IR impurity absorption in Sb2S3–GeS2(Ge2S3) chalcogenide glasses

The IR optical transmission spectra in the 4000–1000 cm⁻¹ (2.5–10 μm) region in the chalcogenide glasses (ChG) of the ternary Ge–Sb–S system of stoichiometric Sb₂S₃–GeS₂ and non-stoichiometric Sb₂S₃–Ge₂S₃ compositions are studied. The compositional dependences of the measured IR spectra connected with influence of O-, H- and C-based absorbed impurites are analyzed.     

Oxygen plasma activation of Cr(CO)6 on α-Fe2O3(0001)

The chemistry of Cr(CO)₆ on the Fe₃O₄(111) surface termination of α-Fe₂O₃(0001) was explored using temperature programmed desorption (TPD), Auger electron spectroscopy (AES), static secondary ion mass spectrometry (SSIMS) and low energy electron diffraction (LEED) both with and without activation from an oxygen plasma source. No thermal decomposition of Cr(CO)₆ was detected on the surface in the absence of O₂ plasma treatment, with first layer molecules desorbing in TPD at 215 K from a close-packed overlayer. The interaction of first layer Cr(CO)₆ with the Fe₃O₄(111)-termination was weak, desorbing only ～ 30 K above the leading edge of the multilayer state. Activation of multilayer coverages of Cr(CO)₆ with the O₂ plasma source at 100 K resulted in complete conversion of the outer Cr(CO)₆ layers, presumably to a disordered Cr oxide film, with Cr(CO)₆ molecules near the surface left unaffected. Absence of CO or CO₂ desorption states suggests that all carbonyl ligands are liberated for each Cr(CO)₆ molecule activated by the plasma. AES and SSIMS both show that O₂ plasma activation of Cr(CO)₆ results in a carbon-free surface (after desorption of unreacted Cr(CO)₆). LEED, however, shows that the Cr oxide film was disordered at 600 K and likely O-terminated based on subsequent water TPD. Attempts to order the film at temperatures above 650 K resulted in dissolution of Cr into the α-Fe₂O₃(0001) crystal based on SSIMS, an observation linked to the Fe₃O₄(111) termination of the surface and not to the properties of α-Cr₂O₃/α-Fe₂O₃ corundum interface. Nevertheless, this study shows that O₂ plasma activation of Cr(CO)₆ is an effective means of depositing Cr oxide films on surfaces without accompanying carbon contamination.     

A Comparative Study of the Growth of Cr on (110)TiO2 Rutile, (0001) α-Al2O3 and (100)SrTiO3 Surfaces

Thin Cr films were deposited on single crystal -Al₂O₃, SrTiO₃ and TiO₂ (rutile) substrates under ultrahigh vacuum conditions using molecular beam epitaxy (MBE). The growth behavior and thermal stability of the films were investigated with scanning tunneling microscopy (STM), X-ray phototelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and transmission electron microscopy (TEM). Cr grew as 3D clusters on all substrates. For all three Cr/oxide systems a strong temperature dependent interfacial reaction was observed. The results suggested that these reactions depended greatly on thermodynamics and on transport properties in the oxide substrates.     

GeO2—Sb2O3—K2O玻璃空芯光纤材料的光学特性研究

系统地研究了传输ＣＯ２激光用的新型光材料ＧｅＯ２－Ｓｂ２Ｏ３－Ｋ２Ｏ玻璃空芯光纤的光学特性。通过理论计算，得到了该材料ｎｒ＜１的波长范围，消光系数Ｋ和损耗数ａ，通过工艺和材料的选择，使ａ理论值达到０．０５ｄＢ／ｍ。同时讨论了ＨＥ１１，ＴＭ０１，ＴＥ０１模式损耗和频率的关系。     

Structure of the (0001) surface of α-Al2O3 from first principles calculations

Fully self-consistent ab initio calculations based on pseudopotentials are used to study the structure and energetics of the basal-plane surface of α-Al₂O₃. The calculated forces on the atoms are used to relax the atomic positions to equilibrium. It is shown that surface relaxations are very large and lead to a reduction of the surface energy by over a factor of two. The results support the validity of earlier work based on pair-interaction models.     

Установка для получения изотоиа В10 методом обменной дистилляции комплекса (CH3)2O.BF3 1)

Zur Gewinnung der Neonisotope in gröβeren Mengen ist die Gegenstromdestillation bei 28 K die geeingnetste Methode. Um das Verfahren ökonomisch durchzuführen, wurden Verdampfer und Kondensator mit dem Neonkältekreislauf gekoppelt. Die Schüttung der KOlonne besteht aus V2A-Wendeln (1,6 mm × 1,8 mm × 0.2 mm) und hat eine Höhe von 6000 mm. Bei zweimaliger Destillation wurden folgende Konzenbtrationen eereicht: für ²²Ne 99,3% (maximal 99,5%), für ²⁰Ne 99,97–99,99%. ²⁴Ne wurde auf 1.2% (d. h. etwa das Vierfache der natürlichen Konzentration) angereichert.