Effect of Bi and Sr concentrations on the formation of the 2223 phase in Bi-Pb-Sb-Sr-Ca-Cu-O materials, obtained under different conditions of thermal treatment

The superconducting properties and the phase and chemical composition of Bi _x Pb_0.3Sb_0.1Sr _y Ca₂Cu₃O_z (x=1.5, 1.6, and 1.7;y=1.9, 2.0, and 2.1) materials synthesized by one-step and multistep thermal treatments have been investigated. The multistep annealing between 825–875°C promotes the 2223 phase. The change of Bi concentration has little effect on the 2223 phase formation, regardless of the kind of thermal treatment used, but increasing the Sr concentration (y> 2) strongly inhibits this phase. It has also been established that the loss of Pb after synthesis depends on the initial Bi concentration. The loss of Pb decreases when the initial Bi content is lower.     

2D Bi2O2Te Semiconductor with Single-Crystal Native Oxide Layer

Following logic in the silicon semiconductor industry, the existence of native oxide and suitable fabrication technology is essential for 2D semiconductors in planar integronics, which are surface-sensitive to typical coating technologies. To date, very few types of integronics are found to possess this feature. Herein, the 2D Bi₂O₂Te developed recently is reported to possess large-area synthesis and controllable thermal oxidation behavior toward single-crystal native oxides. This shows that surface-adsorbed oxygen atoms are inclined to penetrate across [Bi₂O₂]_n²ⁿ⁺ layers and bond with the underlying [Te]_n²ⁿ⁻ at elevated temperatures, transforming directly into [TeO₄]_n²ⁿ⁻ with the basic architecture remaining stable. The oxide can be adjusted to form in an accurate layer-by-layer manner with a low-stress sharp interface. The native oxide Bi₂TeO₆ layer (bandgap of ≈2.9 eV) exhibits visible-light transparency and is compatible with wet-chemical selective etching technology. These advances demonstrate the potential of Bi₂O₂Te in planar-integrated functional nanoelectronics such as tunnel junction devices, field-effect transistors, and memristors.     

Epitaxial growth and thermal-conductivity limit of single-crystalline Bi2Se3/In2Se3 superlattices on mica

Nano Research - Thermal transport in superlattices is governed by various phonon-scattering processes. For extracting the phonon-scattering contribution of hetero-interfaces in chalcogenide...     

Bi2WO6粉体光催化剂的制备方法及研究进展

光催化技术因其在环境污染净化、能源再生方面的应用前景而引起了广泛关注,新型光催化剂钨酸铋因其具有可见光催化活性成为了光化学领域的研究热点之一．作者简述了Bi2WO6粉体光催化剂的结构及光催化性,详细介绍了一些Bi2WO6粉体的制备方法,总结了Bi2WO6粉体光催化剂今后的研究方向与热点,可为有关人员提供参考．     

Truly Concomitant and Independently Expressed Short‐ and Long‐Term Plasticity in a Bi2O2Se‐Based Three‐Terminal Memristor

Concomitance of diverse synaptic plasticity across different timescales produces complex cognitive processes. To achieve comparable cognitive complexity in memristive neuromorphic systems, devices that are capable of emulating short‐term (STP) and long‐term plasticity (LTP) concomitantly are essential. In existing memristors, however, STP and LTP can only be induced selectively because of the inability to be decoupled using different loci and mechanisms. In this work, the first demonstration of truly concomitant STP and LTP is reported in a three‐terminal memristor that uses independent physical phenomena to represent each form of plasticity. The emerging layered material Bi₂O₂Se is used for memristors for the first time, opening up the prospects for ultrathin, high‐speed, and low‐power neuromorphic devices. The concerted action of STP and LTP allows full‐range modulation of the transient synaptic efficacy, from depression to facilitation, by stimulus frequency or intensity, providing a versatile device platform for neuromorphic function implementation. A heuristic recurrent neural circuitry model is developed to simulate the intricate “sleep–wake cycle autoregulation” process, in which the concomitance of STP and LTP is posited as a key factor in enabling this neural homeostasis. This work sheds new light on the development of generic memristor platforms for highly dynamic neuromorphic computing.     

Development and test in grid of 630 kVA three-phase high temperature superconducting transformer

Abstract A 630-kVA 10.5 kV/0.4 kV three-phase high temperature superconducting (HTS) power transformer was successfully developed and tested in a live grid. The windings were wound by hermetic stainless steel-reinforced multi-filamentary Bi2223/Ag tapes. The structures of primary windings are solenoid with insulation and cooling path among layers, and those of secondary windings consist of double-pancakes connected in parallel. Toroidal cryostat is made from electrical insulating glass fiber reinforced plastics (GFRP) materials with room temperature bore for commercial amorphous alloy core with five limbs. Windings are laid in the toroidal cryostat so that the amorphous core operates at room temperature. An insulation technology of double-half wrapping up the Bi2223/Ag tape with Kapton film is used by a winding machine developed by the authors. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests, and it is shown that the transformer meets operating requirements in a live grid. __________ Translated from Proceedings of the CSEE, 2007, 27(27): 24–31 [译自:中国电机工程学报]     

熔盐法合成钛酸铋钾陶瓷粉体

以K2CO3,Bi2O3和TiO2为反应物,KCl为熔盐,通过熔盐法在600℃成功合成纯钙钛矿结构K0.5Bi0.5TiO3(KBT)无铅陶瓷粉体。探寻了制备过程中影响粉体颗粒大小和形貌的工艺参数,并对影响机理进行了探讨。结果表明,与传统固相法相比,熔盐法合成温度显著降低且颗粒平均粒径明显减小。固相法合成的粉体平均粒径为115nm,KCl含量5%和20%的熔盐法合成粉体平均粒径为78nm和67nm。此外,实验发现随着熔盐量的增加,易合成各向异性的棒状粉体。     

Properties of Bi-doped PbTe layers grown by liquid phase epitaxy under controlled Te vapor pressure

Effects of Bi doping in PbTe liquid-phase epitaxial layers grown by the temperature difference method under controlled vapor pressure (TDM-CVP) are investigated. For Bi concentrations in the solution, x_Bi, lower than 0.2 at.%, an excess deep-donor level (activation energy E_d≈0.03–0.04 eV) appears, and Hall mobility is low. In contrast, for x_Bi>0.2 at.%, Hall mobility becomes very high, while carrier concentration is in the range of 10¹⁷ cm⁻³. Inductive coupled plasma (ICP) emission analysis shows that, for x_Bi=1 at.%, Bi concentration in the epitaxial layer is as high as N_Bi=2.3–2.7 × 10¹⁹ cm⁻³. These results indicate that Bi behaves not only as a donor but also as an acceptor, and the nearest neighbor or very near donor-acceptor (D-A) pairs are formed, so that strong self-compensation of Bi takes place. Carrier concentration for highly Bi-doped layers shows a minimum at a Te vapor pressure of 2.2 × 10⁻⁵ torr for growth temperature 470°C, which is coincident with that of the undoped PbTe.     

Sn-8Zn-3Bi无铅焊料的表面改性

采用液相法用有机物改性剂对Sn-8Zn-3Bi焊料进行表面包覆改性,以改善焊料的润湿性能及抗氧化性能。对包覆样品进行了红外光谱表征。考察了样品的抗氧化性、润湿性能和存储性能。结果表明:采用液相法可以实现在Sn-8Zn-3Bi焊料表面包覆有机物。以有机物C为改性剂,且用量为2%(质量分数)时得到的改性样品的润湿角θ为7.8°,铺展面积S为108.83mm2,而未被改性的焊料θ为10.74°,S为93.40mm2。     

吸收栅对光折变晶体钛酸铋中两波混合能量转移的影响

基于钛酸铋晶体的吸收系数依赖于入射光强,考虑吸收栅对它的两波混合能量转移的影响,在某些近似条件下,推导出稳态两波耦合作用的表达式,与实验结果作了比较。测量了纯吸收栅的增益,给出结果。