Syntheses, structures, and magnetic properties of low-dimensional heterometallic complexes based on the versatile building block [(Tp)Cr(CN)3]-

Using the tricyano precursor (Bu(4)N)[(Tp)Cr(CN)(3)] (Bu(4)N(+) = tetrabutylammonium cation; Tp = tris(pyrazolyl)hydroborate), a pentanuclear heterometallic cluster [(Tp)(2)Cr(2)(CN)(6)Cu(3)(Me(3)tacn)(3)][(Tp)Cr(CN)(3)](ClO(4))(3)·5H(2)O (1, Me(3)tacn = N,N',N'-trimethyl-1,4,7-triazacyclononane), three tetranuclear heterometallic clusters [(Tp)(2)Cr(2)(CN)(6)Cu(2)(L(OEt))(2)]·2.5CH(3)CN (2, L(OEt) = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene), [(Tp)(2)Cr(2)(CN)(6)Mn(2)(L(OEt))(2)]·4H(2)O (3), and [(Tp)(2)Cr(2)(CN)(6)Mn(2)(phen)(4)](ClO(4))(2) (4, phen = phenanthroline), and a one-dimensional (1D) chain polymer [(Tp)(2)Cr(2)(CN)(6)Mn(bpy)](n) (5, bpy = 2,2'-bipyridine) have been synthesized and structurally characterized. Complex 1 shows a trigonal bipyramidal geometry in which [(Tp)Cr(CN)(3)](-) units occupy the apical positions and are linked through cyanide to [Cu(Me(3)tacn)](2+) units situated in the equatorial plane. Complexes 2-4 show similar square structures, where Cr(III) and M(II) (M = Cu(II) or Mn(II)) ions are alternatively located on the rectangle corners. Complex 5 consists of a 4,2-ribbon-like bimetallic chain. Ferromagnetic interactions between Cr(III) and Cu(II) ions bridged by cyanides are observed in complexes 1 and 2. Antiferromagnetic interactions are presented between Cr(III) and Mn(II) ions bridged by cyanides in complexes 3-5. Complex 5 shows metamagnetic behavior with a critical field of about 22.5 kOe at 1.8 K.     

Tm3+,Yb3+共掺钨酸钙多晶材料的上转换发光及荧光温度特性

采用高温固相法制备了Tm³⁺,Yb³共掺CaWO₄多晶材料. 980 nm二极管激光器激发下,在可见区获得了¹G₄→³H₆,¹G₄→³H₄,³H₂,³H₃→³H₆ 跃迁产生的上转换荧光. 讨论了Yb³⁺ 离子浓度的变化对Tm³⁺ 的上转换发光强度的影响,同时根据荧光强度比的方法研究了689 和705 nm 红色上转换荧光在313–773 K 范围内的温度特性. 结果表明：基于Tm³⁺,Yb³⁺ 共掺CaWO₄ 多晶材料的红色上转换荧光可以实现温度监测,其测温的最大灵敏度值为5.7×10^-4 K^-1,相应的测量温度为458 K. 关键词： 上转换发光 3+')" href="#">Tm³⁺ 钨酸钙 荧光温度传感     

薄膜硅的变隙问题及隙态分布

用电子束蒸发的方法制备可变光学带隙薄膜硅材料, 给出了研究结果. 介绍了一种做透过率曲线切线确定薄膜光学带隙的简易方法, 给出了制备工艺和条件, 以及各种材料的隙态分布图. 实验发现, 材料的光学带隙宽度不但与量子尺度效应有关, 而且与缺陷形成的势垒高度和宽度以及有序短程(原子串)长度有关; 给出了常规硅材料的光学带隙与原子串长度的关系. 计算表明, 随着原子串长度的加大, 势阱中的电子液面升高, 载流子受缺陷势垒的散射减弱; 在原子串长度较低的情况下, 电子液面不总是随着原子串长度升高, 而是有较大的涨落, 形成锯齿状波动.计算还发现, 在势垒宽度与原子串长度之比不变的情况下, 电子液面还与势垒高度有关. 关键词： 薄膜硅 可变光学带隙 隙态分布 电子液面涨落     

铁电磁体Pb(Fe1/2Nb1/2)O3的磁电性能研究

对铁电磁体Pb(Fe1/2Nb1/2)O3单晶样品中的介电和磁性能进行了研究. 认为在其反铁磁相变点观察到的介电常数和损耗的异常来自于自发极化序和自旋序的相互作用引起的磁电耦合. 磁矩与温度的关系曲线在Néel点以下的低温段呈上升趋势,测得的磁滞回线证明有弱铁磁性出现. 对铁电磁体磁电相互作用的Monte Carlo模拟得到与实验类似的结果.     

Ultrafast carrier dynamics in purified and as-grown single-walled carbon nanotube films

Ultrafast time-resolved optical transmissions in purified and as-grown single-walled carbon nanotube films are measured at a temperature of 200K. The signal of the purified sample shows a crossover from photobleaching to photoabsorption. The former and the latter are interpreted as the state filling and the red shift of the π-plasmon, respectively. The signal of the as-grown sample can be perfectly fitted by a single-exponential with a time constant of 232fs. The disappearance of the negative component in the as-grown sample is attributed to the charge transfer between the semiconducting nanotubes and the impurities.     

Relaxor Behaviour and Ferroelectric Properties of （Li0.12Na0.88） （Nb0.9-xWa0.10Sbx）O3 Lead-Free Ceramics

New lead-free ceramics （Lio.12Na0.88） （Nbo.9-x Ta0.10 Sbx） 03 （0.01 × 0.06） are synthesized by solid-state reaction method. The dielectric, piezoelectric and ferroelectric properties of the ceramics are studied. The dielectric constant dependence with temperature and frequency of the ceramic specimen with x = 0.04 shows typical characteristics of relaxor ferroelectrics, and the Vogel-Fulcher relationship is fulfilled. The dielectric behaviour and its relation to the phase transition phenomena are discussed. The polarization hysteresis loops at room temperature are also measured.     

Synthesis,characterization and application of magnetic-zirconia nanocomposites

In the present study, a magnetic-zirconia nanocomposite was successfully synthesized by a single-step co-precipitation method. The as-prepared nanocomposite was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, and nitrogen sorption measurements. The ultimate material was found to be Fe₃O₄–ZrO₂ nanoparticles with average diameter of 80 nm, high surface area up to 166 m²/g, and strong magnetic property. The application of this new nanocomposite was herein demonstrated by the adsorption of ethyl methylphosphonic acid, a degradation product of nerve agent in water, followed by mass spectrometry detection. Excellent adsorption could be observed, indicating the as-synthesized material was effective to remove phosphonic acid compound from water. Apart from adsorption, the Fe₃O₄–ZrO₂ nanocomposite is promising in various applications such as catalysis and bioseparation.     

用镍硅氧化物源横向诱导晶化的多晶硅薄膜

采用磁控溅射法,以镍硅合金为靶,制备了一种适用于金属诱导横向晶化的氧化物镍源——自缓释镍源.该镍源在内部构成和晶化现象上都不同于纯金属镍源.采用该镍源制备低温多晶硅材料,晶化速率不明显依赖于镍源薄膜的厚度,且晶化多晶硅膜内的残余镍量亦可有效降低,可为薄膜晶体管提供宽的工艺窗口.本文对用纯金属镍源所得多晶硅薄膜的晶化率、表面粗糙度、电学特性等与溅射条件的关系进行了研究,并对相应结果进行了讨论. 关键词： 自缓释 金属诱导横向晶化 多晶硅薄膜 低温制备与退火     

Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector (MPGD), thick GEM with electrodes made of a resistive material (RETGEM) is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar+CO_2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

用镍硅氧化物源横向诱导晶化的多晶硅薄膜

采用磁控溅射法,以镍硅合金为靶,制备了一种适用于金属诱导横向晶化的氧化物镍源——自缓释镍源.该镍源在内部构成和晶化现象上都不同于纯金属镍源.采用该镍源制备低温多晶硅材料,晶化速率不明显依赖于镍源薄膜的厚度,且晶化多晶硅膜内的残余镍量亦可有效降低,可为薄膜晶体管提供宽的工艺窗口.本文对用纯金属镍源所得多晶硅薄膜的晶化率、表面粗糙度、电学特性等与溅射条件的关系进行了研究,并对相应结果进行了讨论.