Microstructure and electrical properties of BaTiO<Subscript>3</Subscript> and (Ba,Sr)TiO<Subscript>3</Subscript> ferroelectric thin films on nickel electrodes

Nickel thin films have been sputtered on standard Si/SiO₂ substrates with TiO₂ as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates were used for deposition of BaTiO₃ and (Ba,Sr)TiO₃ dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates under identical conditions but crystallized in an oxygen atmosphere.     

Fabrication of lead titanate single crystalline nanowires by hydrothermal method and their characterization

Single crystalline nanowires of lead titanate (PbTiO₃) were fabricated by hydrothermal method at 200°C using lead acetate and n-tetrabutyl titanate as starting materials, where sodium hydroxide was served as a mineralizer. Crystalline phases, microstructure and optical properties of PbTiO₃ nanowires were investigated. The PbTiO₃ nanowires were uniform and continuous along the long axis, and were composed of single crystalline PbTiO₃ with a tetragonal perovskite structure. The diameter of a single nanowire was around 12 nm and the length reached up to 3 μm. The chemical composition of the samples and the valence states of elements were determined by X-ray photoelectron spectroscopy (XPS). The ultraviolet/visible absorption spectroscopic investigation suggested that the absorption edge of optical transition of the first excitonic state occurred at around 320 nm. A blue-green light emission peaking at about 471 nm (2.63 eV) is observed at room temperature, and the intensity of this emission increased with increasing excitation wavelength. Oxygen vacancies are responsible for the light emission of PbTiO₃ nanowires.     

YPxV1—xO4（0≤x≤1）：Dy^3＋的合成及其光谱性质的研究

本文报道了不同组成的ＹＰｘＶ１－ｘＯ４（０≤ｘ≤１）：Ｄｙ＾３＋的合成和结构。ＹＰｘＶ１－ｘＯ４（０≤ｘ≤１）为四方晶系，晶胞参数随ｘ的增大呈线性减小。基质的Ｓｔｏｋｅｓ位移随ｘ的增大逐渐变大，而激发光谱峰值则向短波方向移动。在ＹＰｘＶ１－ｘＯ４：０．００６Ｄｙ＾３＋体系中，ｘ＞０．４时出现的基质发射是由ＰＯ＾３－４引起的。基质及Ｄｙ＾３＋的发光效率和Ｄｙ＾３＋的发光强度的黄蓝比均与ｘ有关。同时探     

溶胶—凝胶合成（Mg,Ca）O—SiO2：Eu^3＋,Bi^3＋发光体及其发光行为

以Ｍｇ（ＮＯ３）２，Ｃａ（ＮＯ３）２，Ｅｕ（ＮＯ３）３，Ｂｉ（ＮＯ３）３和Ｓｉ（ＯＣ２Ｈ５）４为反应物，采用溶胶－凝胶法，在比较低的温度，首次合成０．７０１ｍｏｌＭｇＯ－０．１７５ｍｏｌＣａＯ－１．２５ｍｏｌＳｉＯ２：０．０６ｍｏｌＥｕ＾３＋，０．００２ｍｏｌＢｉ＾３＋（加入Ｌｉ＾＋作为电荷补偿剂）发光体，得到了最佳合成条件，研究了由溶胶向凝胶转变和凝胶向发光晶体的转变过程，探讨了发光体在不同激光     

Synthesis of zirconium titanate with an ordered M-fergusonite (beta) structure

We report a new zirconium titanate compound (Zr,Ti)O₂ with 27.5-35 mol% titania (TiO₂) formed from the oxides at 35-38 kbar, 1400-1500 °C. Crystal structure investigations at atmospheric conditions with powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed a monoclinic structure related to that of M-fergusonite (beta). Unit-cell dimensions (from 27.5 to 35 mol% TiO₂): a=7.267(20)-7.340(2) Å, b=10.435(3)-10.429(1) Å, c=5.023(11)-5.040(1) Å, β=136.45(12)-137.55(1)°, V=262.44(92)-260.40(12) Å³, Z=4. Rietveld refinement (R_F=1.55) of a sample with 32.8 mol% TiO₂ indicates that site A is 8-fold coordinated, mostly occupied by Zr, while site B has 6-fold average coordination, occupied by Ti and Zr. Site B is at least partly ordered, as indicated by superstructure reflections 0 0 1 and −2 0 1 detected with TEM, reducing the space group from C2/c to C2. Pronounced streaking of selected diffraction spots is linked to the boundaries of lamellar domains in twin orientation, with twin planes either (200) or (20−2). Adjacent lamellae differ slightly in composition, causing subtle asymmetry of the twin diffraction patterns.     

The effect of B2O3 addition on the crystallization of amorphous TiO2-ZrO2 mixed oxide

The effect of B₂O₃ addition on the crystallization of amorphous TiO₂-ZrO₂ mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO₂-ZrO₂ mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20 wt%. The results indicate that the addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO₂-ZrO₂ into a crystalline ZrTiO₄ compound, while a larger amount of boria (?8 wt%) promotes the crystallization process. FT-IR spectroscopy and ¹¹B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO₄ units delay, while a build-up of trigonal BO₃ promote, the crystallization of amorphous TiO₂-ZrO₂ to form ZrTiO₄ crystals.     

聚苯乙烯—钛酸钡复合材料介电性能的研究

以聚苯乙烯与化学沉淀法钛酸钡陶瓷为基本组成，采用溶液共混，溶液聚合，表面处理后溶液聚合三种方法进行复合，发现后两种复合的钛酸钡颗粒表面发生界面变化，形成活性界面，使得溶液聚合法和表面处理后溶液聚合所得到的材料具有较低的介电损耗，在高频下能保持较高的介电系数。     

Einfache Trithio- und Perthiocarbonatokomplexe mit interessanter Koordinationschemie: [E(CS3)2]2− (E = Sn,Zn, Cd), [E(CS3)3]3− (E = As,Sb, Bi,Co), {Cu(CS3)−}∞ und [Zn(CS4)2]2−

Simple Trithio- and Perthiocarbonato Complexes with Interesting Bond Properties: [E(CS₃)₂]^2? (E = Sn, Zn, Cd), [E(CS₃)₃]^3? (E = As, Sb, Bi, Co), {Cu(CS₃)^?}_∞ and [Zn(CS₄)₂]^2? By reactions of potassium trithiocarbonate ( 1 ) with solutions of zinc(II)- acetylacetonate, cadmium(II)-chloride, tin(II)-chloride, arsenic(III)-sulfide (suspension), antimony(III)-chloride, bismuth(III)-chloride and copper(II)-chloride in dimethyl sulfoxide, as well as of trisodium hexanitrito cobaltate(III) in water, and the precipitation of the complexes with an aqueous solution of tetraphenylphosphonium chloride the compounds (PPh₄)₂[Zn(CS₃)₂] ( 2 ), (PPh₄)₂[Cd(CS₃)₂] ( 3 ), (PPh₄)₂[Sn(CS₃)₂] ( 4 ), (PPh₄)₃[As(CS₃)₃] ( 5 ), (PPh₄)₃[Sb(CS₃)₃] ( 6 ), (PPh₄)₃[Bi(CS₃)₃] ( 7 ), (PPh₄)₃[Co(CS₃)₃] ( 8 ) and (PPh₄)Cu(CS₃) ( 9 ) have been isolated. (PPh₄)₂[Zn(CS₄)₂] · CH₃NO₂ ( 10 ) has been prepared by heating a solution of 2 in nitromethane to 60--70°C in presence of air. The reaction of 1 in dimethyl sulfoxide with an aqueous tetraphenylphosphonium chloride solution in presence of oxygen leads to (PPh₄)₂[C₂S₆] ( 11 ). The compounds have been characterized by spectroscopical studies (IR, Raman, UV/Vis, ¹¹³Cd/⁵⁹Co-NMR), magnetic susceptibility measurements, powder diffractometry, elemental analyses and single crystal X-ray structure analysis ( 4 – 7 , 10 and 11 ). The difficult growing of single crystals has been reported in detail. For crystal data see Inhaltsübersicht.     

Crystallization Temperature Limit of (Ba,Sr)TiO<Subscript>3</Subscript> Thin Films Prepared by a Non Oxocarbonate Phase Forming CSD Route

A new chemical solution deposition (CSD) route for the fabrication of Ba_0.7Sr_0.3TiO₃ (BST) thin films has been developed which completely prevents the formation of an intermediate oxo-carbonate phase. The latter has been reported previously by several authors to be responsible for increased crystallization temperatures. Barium and strontium diaminoethoxides were synthesized starting from pure barium and strontium metal and aminoethanol. These alkoxides were found to be readily soluble in a wide range of solvents and thus were excellent candidates for the CSD process. To prepare a stable precursor solution the aminoalkoxides were dissolved in 2-butoxyethanol and then used for the deposition of BST thin films. We conclude that the minimum crystallization temperature of 600C to be independent of the formation of the oxo-carbonate phase. DTA-TGA were performed on the precursors and their solutions to study their decomposition behaviour. All films annealed at different temperatures were physically characterized by XRD, IR, and SEM. The films prepared by this route at 650C were found to have high dielectric constant and the leakage currents were comparable to BST films prepared by normal carboxylate based routes at 750C.     

Formation of Bi-Sb, Bi-Sn, and Bi-Sb-Sn Nanoclusters in Silica Xerogel Matrices from Mixed-Metal Oxide Precursors

Homogeneous mixed-metal oxides of the general formula (Bi/E/Si)O _x , where E represents a dopant element (E=Sb, Sn, or Sb/Sn), can be prepared using typical sol-gel processing techniques. Reduction of the in-situ Bi(III) and E ions by hydrogen affords nanocomposites of Bi-Sb, Bi-Sn, or Bi-Sb-Sn widely dispersed throughout the silica xerogel matrix. The materials prepared have high Bi-E metal loading of 52–60 wt. % containing Bi-E alloy nanoclusters of 12–15 nm average diameter. These results demonstrate a convenient method for the production of practical quantities of nanostructured bismuth alloy ceramic composites at high metal content.