Crystallization and Microstructure of (Sm, Pb)TiO3 Thin Films Prepared from Sol-Gel Synthesized Solutions

A sol-gel route is developed for the synthesis of samarium modified lead titanate precursor solutions. The solutions are used for the deposition of thin films. After thermal treatment of the films, two crystalline phases are observed by X-ray diffraction analysis: an undesirable pyrochlore phase and a ferroelectric perovskite. These two phases are clearly distinguished in the film microstructure, showing a fined grained fraction of pyrochlore anda-axis oriented rosette grains of perovskite. The development of these phases as well as the evolution of the perovskite/pyrochlore ratio in the films is related to the chemistry of the synthesized solutions and the thermal treatment used for crystallization.     

Optical and Electrical Properties of Ferroelectric SBN Thin Films Prepared by Sol-Gel Process

Strontium barium niobate thin films were prepared by sol-gel method on various substrates using an improved process, two-step heating process. The two-step heating process applies an additive heat-treatment before crystallization for enhancement of the densification and the nucleation of films. Also, highly c-axis oriented SBN thin films with various compositions were obtained on MgO(100) and Pt(100)/MgO(100) substrates. Their optical and electrical properties such as optical propagation loss, refractive index, P-E hysteresis, and dielectric constant, were characterized as a function of the film composition.     

Fabrication and Characterization of Sol-Gel GeO2-SiO2Erbium-Doped Planar Waveguides

GeO2-SiO2 sol-gel planar waveguides doped with Er were deposited by spinning on silica substrates. P2 O5 or Al2O3 were used as co-dopants to improve erbium dissolution in the GeO2-SiO2 matrix. Multilayer amorphous films were obtained at 600 or 700°C.Er ions in the planar waveguide pumped at 980 nm showed fluorescence features around 1530 nm. Narrow fluorescence spectra (20 nm) and long lifetimes (6 ms) were found in P2O5 co-doped samples, whereas Al2O3 co-doping gave wider spectra (50 nm) with slightly lower lifetimes (5 ms). The quenching concentration in the Al2O3 co-doped samples was 0.9 mol% Er.Heat treatments in CCl4 improve the active properties and the addition of Yb enhances the pump absorption efficiency.     

Na0.5La0.5TiO3的水热法合成及其表征

通过控制反应物摩尔比、晶化温度和时间以及体系的碱度等重要因素,用水热法在温和的条件下合成了Na0.5La0.5TiO3;结构分析表明单相的Na0.5La0.5TiO3是具有立方对称性的钙钛矿型化合物,晶胞参数为3.875(。A);初步认为该化合物合成过程为溶解-沉淀机理.     

Preparation and Characterization of MgO Thin Films by a Novel Sol-Gel Method

MgO thin films have been prepared on Si substrates by a novel and simple sol-gel method using magnesium nitrate and collodion as starting material. Solutions consisting of magnesium nitrate in a mixture of collodion and ethanol were spin-coated onto silicon substrates. It was found that collodion was a necessary component to form stable sols and the crystallization and structures were clearly dependent on the amount of the collodion and the annealing temperature. The MgO thin films with good crystallization were obtained after annealing at 800°C. Meanwhile, the microstructure of the MgO films was examined by transmission electron microscopy and atomic force microscopy.     

Sol-Gel Preparation and Photoelectrochemical Properties of Fe2TiO5 Thin Films

Polycrystalline Fe₂TiO₅ films were prepared on nesa silica glass substrates by the sol-gel method, and their photoanodic properties were measured in a three-electrode wet cell with an aqueous buffer solution of pH = 7. Gel films were crystallized into Fe₂TiO₅ when fired at 500°C. The photoanodic current significantly increased when the films were fired at 700°C, and then decreased with increasing firing temperature. Thicker films obtained by repeating the gel film deposition and firing showed smaller photocurrent, and the 50 nm thick film prepared via non-repetitive deposition exhibited the maximum photocurrent. Although the photoresponse was extended to wavelengths near 500 nm, the maximum quantum yield was as low as 0.12 at a wavelength of 340 nm.     

Synthesis of Bi2O3 and Bi4(SiO4)3 Thin Films by the Sol-Gel Method

Bi2O3 thin films were prepared by dipping silica slides in ethanolic solutions of tris(2,2-6,6-tetramethylheptane-3, 5-dionato)bismuth(III) [Bi(dpm)3] [1] and heating in air at temperatures 500°C. Bi4(SiO4)3 homogeneous thin films were obtained from the reaction of the bismuth oxide coating with the silica glass substrate at temperatures higher than 700°C. For heat treatments at temperatures between 600°C and 700°C, Bi2SiO5 coatings were obtained. The composition and microstructure evolution of the films were determined by Secondary Ion-Mass Spectrometry (SIMS), X-Ray Photoelectron Spectroscopy (XPS) and Glancing Angle X-Ray Diffraction (GA-XRD). The synthesis procedure was reproducible and allowed the control of the Bi2O3 phase composition. Moreover, the thin film annealing parameters were correlated with the formation of bismuth silicates, among which Bi4(SiO4)3 (BSO) is very appealing for the production of fast light-output scintillators [2].     

Crystalline,Highly Oriented MOF Thin Film: the Fabrication and Application

The thin film of metal‐organic frameworks (MOFs) is a rapidly developing research area which has tremendous potential applications in many fields. One of the major challenges in this area is to fabricate MOF thin film with good crystallinity, high orientation and well‐controlled thickness. In order to address this challenge, different appealing approaches have been studied intensively. Among various oriented MOF films, many efforts have also been devoted to developing novel properties and broad applications, such as in gas separator, thermoelectric, storage medium and photovoltaics. As a result, there has been a large demand for fundamental studies that can provide guidance and experimental data for further applications. In this account, we intend to present an overview of current synthetic methods for fabricating oriented crystalline MOF thin film and bring some updated applications. We give our perspective on the background, preparation and applications that led to the developments in this area and discuss the opportunities and challenges of using crystalline, highly oriented MOF thin film.     

Textured PbTiO3, Pb(Ca)TiO3-Al2O3 Composite Films Prepared by Chemical Solution Deposition Method

Chemical solution deposition method (CSD) method was used to prepare PbTiO₃ (PT), Pb_{1– x} Ca _x TiO₃ (PCT), PbTiO₃-Al₂O₃ (PT-AL) and Pb_{1 – x} Ca _x TiO₃-Al₂O₃ (PCT-AL) thin films on amorphous (soda-lime glass, SiO₂ glass) substrates. The films were examined by XRD methods to describe the phase composition, cell parameters, type and degree of texture. In dependence on the molar ratio of Ti:Al, the different extent of crystallographic ordering was observed ranging from randomly oriented to strongly textured crystallites of PT. (100)uvw preferred orientation growth of PT grains was identified.     

磷酸铁纳米薄膜复合光波导氨气传感元件的制备

将硝酸铁和甲醇、磷酸溶液按一定比例混合后,通过旋涂法制备了磷酸铁（FePO₄）纳米薄膜,测定了匀胶机转速对膜厚及烘干温度对膜厚和折射率的影响,并发现薄膜的烘干温度超过150 ℃时,薄膜的厚度（130 nm）和折射率(1.7)变化不大。将该薄膜固定在钾离子交换玻璃光波导表面,研制出FePO₄膜/K⁺交换玻璃复合光波导。酸碱指示剂溴百里酚兰（BTB）作为敏感试剂,固定在复合光波导表面,研制了BTB膜-FePO₄膜/K⁺交换玻璃复合光波导氨气传感元件。采用自装的光波导气体传感检测系统对不同浓度的氨气进行了检测。结果表明,该传感元件能够检测0.35 mg/m³浓度的氨气,并具有响应（10 s）及恢复（90 s）速度快、可逆性好、连续使用等特点。     

Processing and Characterization of Sol-Gel Derived Modified PbTiO3 for Ferroelectric Composite Applications

Powders of (Pb_0.8Ca_0.2)(Ti_0.99Mn_0.01)O₃ have been prepared by sol-gel processing. A tetragonal phase is formed after heat treatment at as low as 800°C. The tetragonality was found to be 1.053±0.005 and Curie temperature 315°C. Composite films with 0–3 connectivity were prepared from 800°C heat treated powders and P(VDF-TrFE) by the solvent casting technique. Composites poled at 20 MV/m, exhibited a pyroelectric coefficient of 17.4 μC/m²K and a pyroelectric figure of merit (FOM_p=p/ε) of 0.51 μC/m²K.     

Y2O3薄膜/锡掺杂玻璃光波导气敏元件及其气敏性

采用溶胶-凝胶法将氧化钇(Y2O3)敏感膜固定在锡掺杂玻璃光波导表面,研制出了Y2O3薄膜/锡掺杂玻璃光波导气敏元件,并对挥发性有机气体进行了检测.通过XRD测试对敏感薄膜的结构及晶粒尺寸进行了表征.实验结果表明,在室温下Y2O3薄膜/锡掺杂玻璃光波导气敏元件对二甲苯、氯苯气体有较好的选择性响应,其响应浓度范围为l×10-3 ～1×10-5(V/V).Y2O3薄膜/锡掺杂玻璃光波导气敏元件具有灵敏度高、成本低、响应速度快、制作工艺简单和可逆性好等优点.     

Preparation and Characterization of (Ba,Ca)(Ti,Zr)O3 Thin Films Through Sol-Gel Processing

(Ba_0.92,Ca_0.08)(Ti_0.92,Zr_0.08)O₃ thin films were prepared from Ba-Ti and Ca-Zr precursors by sol-gel processing. Polymerizable solutions containing Ba-Ti and Ca-Zr, respectively, were newly synthesized. Decomposition of the starting compounds and crystallization behavior of the film were examined by using TG/DTA and XRD. Microstructure of thin films was observed by using SEM. Polycrystalline (Ba_0.92,Ca_0.08)(Ti_0.92, Zr_0.08)O₃ films obtained by firing at 800°C were dense with fine grains. The thin films showed a dielectric constant of 1200 and dielectric loss of 0.5%.     

溶胶-凝胶法制备桥式聚倍半硅氧烷/SiO2光学防潮膜

采用溶胶-凝胶法, 以首次合成的具有桥式结构的间苯二亚甲基二脲基丙基三乙氧基硅烷(m-XDUPTEOS)和正硅酸乙酯(TEOS)为前驱体, 共同水解缩聚制备了不同摩尔配比的桥式聚倍半硅氧烷/SiO₂杂化溶胶, 并旋涂制膜. 通过UV-Vis, AFM和TGA对薄膜的光学性能、表面形貌和热稳定性进行了分析. 结果表明, 该薄膜平整均匀、具有良好的光学透明性、热稳定性和防潮性能.     

Preparation and Optical Properties of Gold-Dispersed BaTiO3, PGO (Pb5Ge3O11) and PLT (Pb1-1.5xLaxTiO3) Thin Films by Sol-Gel Process

Gold-dispersed BaTiO₃, PGO and PLT thin films, which will be used for third-order nonlinear optical devices, were prepared by sol-gel process with spin-coating using HAuCl₄4H₂O, Ba(CH₃COO)₂, Ti[O(CH₂)₃CH₃]₄, Pb(CH₃COO)₂3H₂O, Ge[O-n-C₄H₉]₄, La(CH₃COO)₃1.5 H₂O as starting materials. The thin films were heat-treated in air at temperatures ranging from 400 to 800 for 1 h. The nonlinear optical property of these thin films was measured by the degenerate four-wave mixing (DFWM) method using a frequency-doubled Nd: YAG laser with 20 ps pulse duration. Third-order nonlinear susceptibility χ⁽³⁾ of gold-dispersed BaTiO₃, PGO and PLT thin films with 5 vol% of gold were 1.410⁻⁶ esu, 3.510⁻⁷ esu respectively. The large χ⁽³⁾ may be ascribed to the high dielectric constant of the films.     

Structural and Optical Properties of Sol-Gel Derived Aluminosilicate Planar Waveguides Doped with Er3+ Ions

Er3+ doped-aluminosilicate thin films were prepared on silica and silica/Si substrates by the sol-gel process and dip-coating. The sol-gel aluminosilicate planar waveguides were prepared from silicon and aluminium alkoxides. Their structural characterization has been carried out by Raman spectroscopy, Atomic Force and Scanning Electron Microscopies. The results indicated that these films present an amorphous structure until an annealing temperature of 900°C, while at temperatures higher than 1000°C, crystallization occurs. An estimate of microcrystallite sizes using Raman spectroscopy is given, which agrees with data from scanning electron microscopy. The optical properties have been investigated by Fluorescence spectroscopy in the visible region.     

Multielement XRF Semimicroanalysis of Pb(Zr,Ti)O3 Type Ferroelectric Ceramic Materials Doped with Pb(Nb,Mn)O3 and Bi2O3 by the Thin Layer Method

A method of wavelength-dispersive XRF analysis of Pb(Zr,Ti)O₃ type ferroelectric ceramics doped with Pb(Nb,Mn)O₃ and Bi₂O₃ is presented. The major elements Pb, Zr, Ti and minor elements Nb, Mn, Bi were determined. Matrix effects were minimized by using the thin layer method. Standards of the same chemical composition but varied masses were prepared to simplify calibration. To minimize errors resulting from inhomogeneity of a mass per unit area, the internal standard was used. Preparation of the sample consisted in digesting 25mg of the materials (with nickel as the internal standard) in sulfuric acid, evaporating to dryness and digesting in nitric acid and hydrogen peroxide, filling up to 25mL, and dropping 0.5mL of the solution onto a substrate. Standard samples were prepared by dropping different amounts of the multielement solution onto the substrate. The residual standard deviation for the reference sample of mass from 0.25mg to 0.7mg was within the range of 0.001–0.009mg (correlation coefficient 0.998–0.999) for major elements and within the range of 0.00003–0.0009mg (correlation coefficient 0.989–0.993) for minor elements. The detection limits for 0.5mg samples were within the range of 0.015%–0.35% for manganese and zirconium, respectively.     

Preparation and Properties of Highly Oriented Sr0.3Ba0.7Nb2O6 Thin Films by a Sol-Gel Process

We succeeded in the preparation of epitaxial or highly oriented strontium-barium niobate (Sr_0.3Ba_0.7Nb₂O₆) thin film by a sol-gel process. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)₅ as raw materials, and acetic acid and diethylene glycol monomethyl ether as solvents. Sr_0.3Ba_0.7Nb₂O₆ film sintered at 900°C on MgO(1 0 0) was oriented with c-axis perpendicular to the substrate surface. Sr_0.3Ba_0.7Nb₂O₆ film sintered at 700°C on SrTiO₃(1 0 0) was an epitaxial and oriented with c-axis in parallel to the substrate surface. Transmittance of Sr_0.3Ba_0.7Nb₂O₆ film (film thickness: 144 nm) was more than 60% at the range from 400 to 800 nm. Refractive index was 2.33 at 633 nm. Dielectric constant and dielectric loss of the Sr_0.3Ba_0.7Nb₂O₆ thin films prepared on polycrystal Pt substrates were 600 and 0.06 at room temperature and 1 kHz, respectively. The curie temperature (T_c) of polycrystalline Sr_0.3Ba_0.7Nb₂O₆ thin films was about 200°C. At room temperature and 50 kHz, remanent polarization (P_r) and coercive field (E_c) of the polycrystalline thin films were 1.79 C/cm² and 2.69 kV/cm, respectively.     

Electrical and Optical Properties of MgO Thin Film Prepared by Sol-Gel Technique

MgO thin films with either (111) or (200) preferential orientation have been prepared on (100) Si substrates by sol-gel method after a heat-treatment at 800°C. The obtained (111) preferentially oriented MgO film has a dielectric constant of 7.0 with a loss factor of 5% and a dielectric strength higher than 8 × 10⁵ V/cm. The optical refractive index, which depends on the film thickness, is 1.71 when the film thickness is 260 nm. The surface structure of the Si substrate is believed to affect the preferential orientation of the sol-gel derived MgO film. Specifically, the microstructures at the interface indicate an interdiffusion of Mg, O, and Si between the film and the substrate.     

Synthesis,Ferroelectric and Optical Properties of (Pb,Ca)TiO3 Thin Films by Soft Solution Processing

Calcium modified lead titanate sol was synthesized using a soft solution processing, the so-called polymeric precursor method. In soft chemistry method, soluble precursors such as lead acetate trihydrate, calcium carbonate and titanium isopropoxide, as starting materials, were mixed in aqueous solution. Pb_0.7Ca_0.3TiO₃ thin films were deposited on platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure, dielectric and optical properties of the thin films were investigated. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) capacitors. The typical measured small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 299 and 0.065, respectively, for a thin film with 230 nm thickness annealed at 600°C for 2 h. The remanent polarization (2P_r) and coercive field (E _c) were 32 C/cm² and 100 kV/cm, respectively. Transmission spectra were recorded and from them, refractive index, extinction coefficient, and band gap energy were calculated. Thin films exhibited good optical transmissivity, and had optical direct transitions. The present study confirms the validity of the DiDomenico model for the interband transition, with a single electronic oscillator at 6.858 eV. The optical dispersion behavior of PCT thin film was found to fit well the Sellmeir dispersion equation. The band gap energy of the thin film, annealed at 600°C, was 3.56 eV. The results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of PCT thin films.