Effect of chelating agents on the preferred orientation of ZnO films by sol-gel process

The effect of chelating agents of ZnO precursor solutions on crystallization behavior was investigated. Two different additives, monoethanolamine (MEA) and diethanolamine (DEA), and crystalline Pt (111)/Si and amorphous SiN _x /Si substrates, were used for this study. ZnO film grown on SiN _x /Si from a DEA-chelated precursor solution shows a poorly oriented microstructure with weak crystallization peaks, while ZnO film grown on Pt(111)/Si shows a c-axis preferred orientation. In the case of ZnO films prepared with a MEA-chelated precursor solution, all films show a strong preferred orientation irrespective of substrate type. This result clearly demonstrates the role of the chelating agent on the crystallographic orientation and crystallization behavior of sol-gel processed ZnO films.     

溶胶-凝胶法制备适用于还原性气氛下烧结的钛酸钡基超细粉体

以醋酸钡、钛酸四丁酯和冰醋酸为主要原料,采用溶胶-凝胶方法制备出适用于还原气氛下烧结的超细钛酸钡基陶瓷粉体.利用差热分析研究了前驱体的热转变过程.利用XRD分析了在不同烧结温度下,粉体的相结构.利用透射电镜研究了温度对粉体粒度和形貌的影响.实验结果表明,所得干凝胶在600℃度煅烧后就可以得到均匀且均相的掺杂改性钛酸钡粉体.在700℃度煅烧1h后,就可以得到形貌规则,粒度为100nm左右的高纯掺杂改性钛酸钡粉体.     

溶胶-凝胶法制备钛酸钡陶瓷纤维

首次采用乙酰丙酮作为钛醇盐的稳定剂，醋酸钡和钛酸丁酯为原料，无水乙醇-冰醋酸作为溶剂，用sol-gel法制备了长达50cm的BaTiO3凝胶纤维。用FT-IR、XRD、TGA．DTA、SEM等手段对凝胶纤维或陶瓷纤维进行一系列表征，最终得到单一钙钛矿相钛酸钡陶瓷纤维，纤维直径4～10μm，具有椭圆形截面。     

BaTiO3 thin film prepared by coating-pyrolysis process on Nb-doped SrTiO3 substrate

Epitaxial BaTiO3 thin film was prepared on Nb-doped SrTiO3 substrate by coating-pyrolysis process using a mixed solution of barium and titanium naphthenates. The amorphous film pyrolyzed at 470 °C was crystallized with high orientation after heat-treatment at 850 °C under low oxygen partial pressure. X-ray diffraction /2 and scans indicated that the BaTiO3 film was epitaxial relationship with Nb-doped SrTiO3 substrate. The dielectric constant was approximately 230 at 103 Hz and was monotonically decreased with increasing of frequency at room temperature.     

由溶胶-凝胶法制备的掺氧化钼的氧化钨薄膜的电致变色性能

钨粉和钼粉在过氧化氢的作用下生成氧化钨和氧化钼的溶液，加入冰乙酸进行酸化，然后在60℃下烘干，用适量的乙醇配得氧化钨和氧化钼母液。用ITO玻璃在该溶液浸泡后拉出并在150℃下烘干1h，便得到掺有氧化钼的氧化钨薄膜。X射线衍射（XRD）显示所得的薄膜为非晶态结构，扫描电镜（SEM）发现整个薄膜的表面较为平滑，但在极其微小的局部仍有裂纹颗粒生成。薄膜的伏安特性显示薄膜对锂离子具有一定的存储能力，其光的透过率测量表明溶胶-凝胶制备的掺有氧化钼的氧化钨薄膜对光具有很好的调节作用。     

溶胶-凝胶法有机-无机杂化材料的制备及应用研究进展

介绍了溶胶-凝胶法制备有机-无机杂化材料的原理、分类和制备方法,对杂化材料性能研究的表征手段和应用领域进行了简要的论述,这类性能优异的新材料在未来的高科技领域,具有广阔的应用与开发前景。     

Sol-gel法制备NiZnCu铁氧体性能的研究

采用溶胶-凝胶自燃法制备了Ni0.4Zn0.4Cu0.2Fe2O4铁氧体,使用HP4191A阻抗分析仪测试了材料高频磁谱;结合快速热处理(RTP)工艺制备了Ni0.4Zn0.4Cu0.2Fe2O4磁性薄膜,使用AFM、XRD、AGM系统地研究了制备工艺对薄膜样品表面形貌、晶相结构和准静态磁性的影响。测试结果表明:Ni0.4Zn0.4Cu0.2Fe2O4可适用于射频领域,截止频率fr在1GHz以上,1GHz处起始磁导率μ′=5.3,μ″=3.45;sol-gel法制备磁性薄膜最佳晶化温度为600℃左右,在此温度下制备的薄膜晶粒大小为13nm左右,饱和磁化强度Ms=2.29×105A/m,矫顽力Hc=1.24×103A/m。     

热处理对溶胶凝胶MoO3薄膜特性的影响

报道了以钼粉为原料,采用溶胶凝胶技术和旋转镀膜方法,制备MoO3纳米薄膜。采用TG-DSC分析、X射线衍射仪(XRD)、原子力显微镜(AFM)、红外光谱仪等方法分析了薄膜的特性。研究结果表明MoO3薄膜具有纳米颗粒结构,热处理使得MoO3颗粒长大,且表面平整度降低;XRD分析显示,250℃热处理的MoO3粉末已结晶(为α-MoO3),且沿(Ok0)方向取向强烈;随热处理温度的升高,MoO3微结构发生了相应的变化,Mo——O（2）、Mo——O（3）键振动吸收增强,且峰位移动。这些变化归因于热处理导致的MoO3颗粒形状、团聚状态的变化以及应变键的产生。     

Modified sol-gel process for the preparation of BaTiO3 and PbTiO3 ferroelectric films

A modified method for preparing barium and lead titanate films is suggested, which combines precipitation from solution and elements of sol-gel processing. The ∼1-μm-thick BaTiO₃/Pt and PbTiO₃/Pt films deposited on Pt foil are transparent, show good adhesion, and have the 1 : 1 : 3 stoichiometry. The films are finegrained, with a mean grain size of 0.1–0.2 μm. The barium titanate films are characterized byt _C = 110-125°C, ε₂₀ = 167-500, tanδ₂₀ = 0.015-0.06, ε_max = 1050,P _s= 3.2 μC/cm²,E _c = 14 kV/cm, ρ = (5-7) × 10⁹ Ω cm, andV _br = 80-150 kV/cm. The lead titanate films are characterized byc/a = 1.056, ε₂₀ = 105-110, tanδ₂₀ = 0.11-0.16,P _s = 4.1 μC/cm²,E _c = 34 kV/cm, ρ = (0.8-3.0) × 10⁹ Ω cm, andV _br = 50-100 kV/cm.     

Preparation of multiple oxide BaTiO3 fibres by the sol-gel method

Multiple oxide BaTiO₃ gel fibres were prepared by the sol-gel method from Ba(OC₂H₅)₂-Ti(O-isoC₃H₇)₄-H₂O-C₂H₅OH-CH₃COOH and Ba(CH₃COO)₂-Ti(O-isoC₃H₇)₄-H₂O-CH₃COOH solutions. Relatively long gel fibres of 10cm length were obtained from both solutions in the limited composition region. The latter solution in particular showed a spinnability even when it contained no water. Therefore, the occurrence of spinnability of the solution was considered to be due to the formation of linear polymers composed of bridging acetate groups such as TiO-C(CH₃)-O-Ti rather than metalloxane bonding as Ti-O-Ti. Addition of water to the solutions seems to break the bridging acetate bonds and replace some of them by bridging oxygen bonds. The as-drawn gel fibres which were X-ray amorphous crystallized into BaTiO₃ ceramic fibres of 5mm average length upon heating above 600 ° C. However, the gel fibres drawn from the sols without water became powdery on heating because of the lack of Ti-O-Ti metalloxane bonds. The crystallization behaviour of the BaTiO₃ gel fibres is discussed based on the infrared spectroscopy, X-ray diffraction analysis and thermogravimetric-differential thermal analysis.     

溶胶-凝胶法制备镁蔷薇辉石的体外生物活性研究

用溶胶-凝胶法制备出纯相镁蔷薇辉石(Ca3MgSi2O8)粉体,并在10MPa的轴向压力下,将其压制成尺寸为Ф10mm×5mm的圆柱状块体,通过模拟体液浸泡对其体外生物活性进行研究.用X射线衍射(XRD)及扫描电镜(SEM)分别对粉体以及浸泡后形成的羟基磷灰石(Hap)的物相和表面形貌进行表征.结果表明:在约1400℃的煅烧温度下可以得到纯相镁蔷薇辉石粉体,其粒径约为1～3μm;圆柱状镁蔷薇辉石在模拟体液浸泡7d后就能明显检测到表面有羟基磷灰石生成,浸泡14d后呈结晶较好的蠕虫状结构.因此,溶胶-凝胶法合成的镁蔷薇辉石具有良好的诱导羟基磷灰石形成能力和体外生物活性.     

基于溶胶-凝胶法制备BaTiO3基PTCR纳米陶瓷粉体研究

以溶胶-凝胶法制备了BaTiO3基PTCR纳米陶瓷粉体，通过适当控制材料的掺杂量和烧成制度达到细化晶粒、降低烧结温度及降低室温率的目的。讨论了溶胶．凝胶过程中水的加入量、乙酸加入量、乙醇加入量、成胶温度对形成细晶粉体的影响，制备出的BaTiO3粉体具有纯度高、粒径小、均匀性好、活性高、热处理温度低等优点。R-T丁曲线表明1260℃较1240℃烧结具有高的升阻比、温度系数，低的电阻率、居里温度：XRD分析表明所得粉体与BaTiO3主峰相吻合；800℃预烧2h所得BaTiO3粉体的TEM图表明粉体分布较均匀、外形为近似球形，其平均晶粒尺寸约30nm左右，与XRD得到的晶粒相当，单个颗粒是单晶；1240℃下烧结所得样品的SEM图片看出样品的平均晶粒约1～2μm、晶粒较为均匀致密。     

Low temperature evolution of crystalline BaTiO3 from alkali-metal free precursor using sol-gel process

 Bulk structure and surface texture of BaTiO₃ materials synthesized at low temperature using sol-gel technique have been investigated. The materials were produced by the pyrolysis of an xerogel precursor of the tentative formula BaTiO_3-x(CH₃COO)_2x, which was prepared using 1:1 molar ratio of barium acetate and titanium oxyacetate solution. The present method avoids using alkali-metal hydroxides (as a hydrolyzing agent), and thus produces an alkali-metal free precursor. The decomposition course of the xerogel at the onset of formation of crystalline BaTiO₃ was probed applying thermogravimetry (TG), differential scanning calorimetery (DSC), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques. Results indicated that most of the precursor weight loss occurs below 400°C, with the formation of titania rich intermediates. However, it was not until the temperature reached ≥600°C that well crystallized BaTiO₃ was produced. The specific surface area and porosity were assessed for BaTiO₃ produced at 600–1000°C using N₂ adsorption at liquid N₂ temperature. Received: 21 July 1998 / Reviewed and accepted: 30 September 1998     

Photochromism of spiropyran and diarylethenedoped silica gels prepared by the sol-gel process

Spiropyran and diarylethene were doped in silica gels which were prepared from Si(OCH₃)₄ and Si(OC₂H₅)₄, respectively, and their photochromic properties were compared. In the gels, both organics are incorporated with open modifications and show the photochromism between red and colourless modifications. The closed form of spiropyran, which is converted from the open one by irradiation with light, is thermally backed into the open form after the light is blocked. The activation energy of thermochemical reaction is 0.86 eV. Diarylethene shows no thermochemical reaction below 140°C, but shows a photochemically reversible change on alternate irradiation by light of 436.5 and 578 nm.     

ZnO thin films prepared by a single step sol-gel process

ZnO thin films were prepared on fused silica from a single spin-coating deposition of a sol-gel prepared with anhydrous zinc acetate [Zn(C₂H₃O₂)₂], monoethanolamine [H₂NC₂H₄OH ] and isopropanol. Crystallization annealing was performed over the range 500 to 650 °C. X-ray analysis showed that thin films were preferentially orientated along the [002] c-axis direction of the crystal. The films had a transparency of greater than 85% in the visible region for sol-gels with a zinc content of up to 0.7 M and exhibited absorption edges at ∼ 378 nm. The optical band-gap energy was evaluated to be 3.298-3.306 eV. Photoluminescence showed a strong emission centered at ca. 380 nm along with a broad yellow-orange emission centered at ca. 610 nm. Single step sol-gel thin film deposition in the film thickness range from 80 nm to 350 nm was demonstrated. The effect of sol-gel zinc concentration, film thickness and crystallization temperature on film microstructure, morphology and optical transparency is detailed. A process window for single spin coating deposition of c-axis oriented ZnO discussed.     

Alcohol sensing of tin oxide thin film prepared by sol-gel process

The present paper describes the alcohol sensing characteristics of spin coated SnO₂ thin film deposited by using sol-gel process. The sensitivity of the film was measured at different temperatures and different concentrations of alcohol at ppm level. Alcohol detection result shows peak sensitivity at 623 K. The variation of sensitivity and ethanol concentration has shown a linear relationship up to 1150 ppm and after that it saturates. The response time measurement of the sensor was also observed and it was found that the response time is 30 sec. The results obtained favour the sol-gel process as a low cost method for the preparation of thin films with a high sensing characteristic.     

微弧氧化法制备BaTiO3薄膜的结构特性

利用微弧氧化技术在钛衬底上制备了钛酸钡铁电薄膜.利用x射线(XRD)、扫描电镜(SEM)和能谱仪(EDS)等手段研究了电流密度和电解液浓度对微弧氧化薄膜的化学成分、相组成、结构和表面形貌的影响.结果表明,随着电流密度和电解液浓度的增加,BaTiO3的形成能力增强,薄膜的致密度下降,表面粗糙度增加;当Ba(OH)2浓度为0.2 mol/l,电流密度为5 A/cm2,微弧氧化反应18 min后,可获得具有较高简单四方结构和底心正交结构BaTiO3含量的薄膜,且薄膜与衬底具有良好的结合性能.     

Structural study of lithium titanium mixed oxides prepared by sol-gel process

A structural study, using TGA-DSC analysis, X-ray diffraction, Raman scattering and FT Infrared absorption, is performed on mixed titanium lithium oxide with 20% of lithium prepared by sol-gel process. The structure is investigated as a function of the annealing temperature. At low temperatures the sample is in the anatase phase and transforms to the rutile phase near 500°C. The crystallite size of rutile TiO₂ increases from 40 to 100 nm as the temperature increases. However the size increase presents some discontinuity at temperature around 600°C. At thermal treatment temperatures from 500°C to 850°C the presence of LiTi₂O₄ in the sample is clearly observed. Finally at 1000°C the sample is composed by a mixture of rutile TiO₂ and Li₂Ti₃O₇.