Concentration effect on fluorescent characteristics of Ti:Al2O3 crystal

Concentration dependent spectra and fluorescence lifetime of the upper state ²E_g of Ti³⁺ ion in titanium doped sapphire crystal were measured at room temperature with the doped level from 0.03 to 0.44 wt% Ti₂O₃. A weak concentration quenching effect on Ti:Al₂O₃ crystal fluorescence was demonstrated, and the experimental results were not inconsistent with the theoretical prediction calculated from Förster-Dexter theory of resonance energy transfer.     

High-resolution and analytical transmission electron microscopy of epitaxial YBa2Cu3O7−x thin films and YBa2Cu3O7/PrBa2Cu3O7 superlattices

Transmission electron microscopy (TEM) studies of epitaxial YBa₂Cu₃O_7−x thin films and YBa₂Cu₃O₇/PrBa₂Cu₃O₇ superlattices are summarized. High-resolution imaging of cross-sections and plan views and energy-dispersive X-ray microanalysis and electron energy loss spectroscopy in the transmission electron microscope were the methods applied. In the first section results on YBa₂Cu₃O_7−x thin films With varying oxygen stoichiometry deposited onto SrTiO₃ are discussed. Then, YBa₂Cu₃O₇/PrBa₂Cu₃O₇ superlattices deposited onto SrTiO₃ and MgO are investigated. Finally, an interface analysis of high-quality YBa₂Cu₃O_7−x thin films deposited onto sapphire with yttrium-stabilized zirconia buffer layers is presented.     

缺陷对β-Ga2O3薄膜的结构和光学特性的影响

采用射频磁控溅射技术和后期退火在蓝宝石衬底上成功制备了β-Ga₂O₃薄膜。借助于X射线衍射(XRD)、拉曼散射光谱(Raman)、X射线光电子能谱(XPS)、以及二次离子质谱(SIMS)研究了缺陷对β-Ga₂O₃薄膜的结构和光学特性的影响。结果表明,未退火的Ga₂O₃薄膜呈现非晶态,随高温退火时间逐渐增加,非晶Ga₂O₃薄膜逐步转变为沿(-201)方向择优生长的β-Ga₂O₃薄膜。所有Ga₂O₃薄膜在近紫外到可见光区的平均透过率都高达95%,β相Ga₂O₃薄膜的光学带隙比非晶态薄膜增加~0.3 eV,且随退火时间的增加,β-Ga₂O₃薄膜的光学带隙也随之变宽。此外,发现非晶Ga₂O₃薄膜富含氧空位缺陷,高温退火处理后,β-Ga₂O₃薄膜中的氧空位浓度明显降低,但蓝宝石衬底中的Al极易扩散至Ga₂O₃薄膜层,并随退火时间的增加Al浓度明显增加,氧空位的降低和Al杂质的增加是导致β-Ga₂O₃薄膜光学带隙变宽的主要原因。     

Preparation and photoelectrochemical properties of Ti1−xVxO2 solid solution thin film photoelectrodes with gradient bandgap

A design of a gradient bandgap Ti_1−xV_xO₂ thin film electrode for wet-type solar cells is provided. The gradient bandgap film electrodes were prepared by heating stacked layers of varying V/Ti ratios using the sol-gel method. A composition gradient was observed for some of the samples by X-ray photoelectron spectroscopy although it was not very large. For the Ti_1−xV_xO₂ film electrodes, conspicuous visible light photoresponse and photoelectrochemical stability were observed. The photocurrent increased with increasing bias potential. However, the photocurrent onset potentials of the Ti_1−xV_xO₂ film electrodes were more positive than those of TiO₂ film electrodes, probably owing to the high surface state density introduced by the diffusion of vanadium ions.     

Investigation of thermal stability, phase formation, electrical, and microstructural properties of sputter-deposited titanium aluminide thin films

Titanium aluminide thin films are being considered as coating materials for high temperature applications due to their high melting points and high oxidation resistance. In this study, Ti₃₇Al₆₃ and Ti₅₃Al₄₇ thin films are deposited onto SiO₂ substrates by RF magnetron sputtering using compound targets and then annealed in vacuum to investigate the properties of the films. Rutherford backscattering spectrometry, X-ray diffractometry, transmission electron microscopy, and four-point probe measurements are used to analyze the characteristics of Ti₃₇Al₆₃ and Ti₅₃Al₄₇ thin films for high temperature electronics applications. The films show good thermal stability up to 700 °C for 1 h in vacuum. Reasonable resistivity is obtained when appropriate compositions and anneal conditions are used.     

Ti3AlC2-Al2O3/TiAl3复合材料在Al液中的熔蚀-磨损行为及其交互作用机制

通过对比分析Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在纯腐蚀、纯磨损及熔蚀-磨损三种条件下的材料流失特征,研究了Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中的熔蚀-磨损行为及熔蚀与磨损的交互作用机制。结果表明,Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中的熔蚀-磨损体积损失比H13钢的体积损失低了两个数量级,随着载荷和转速的上升,Ti₃AlC₂-Al₂O₃/TiAl₃复合材料的磨损由磨粒磨损逐渐向黏着磨损转变。Ti₃AlC₂-Al₂O₃/TiAl₃复合材料的熔蚀、磨损交互作用率的最大值为47.5%,在低载荷或低转速条件下由于铝熔体的润滑作用,Ti₃AlC₂-Al₂O₃/TiAl₃复合材料甚至表现出负的交互作用。这一方面是由于Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中腐蚀时不生成其它界面产物,而仅为极少量Ti元素的溶解;另一方面则是由于TiAl₃基体与Al₂O₃二者所形成的空间网络状结构改善了Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中的耐磨损性能。      

Structural and optical properties of yttria-stabilized-zirconia films grown by MOCVD

The morphology of yttria doped zirconia thin films deposited by metal organic chemical vapour deposition (MOCVD) in two different substrate materials, glassy quartz and sapphire single crystals has been examined. The Y₂O₃ doping concentration has been varied from 3 to 12 mol percent. Structural characterization has been realized by X-ray diffraction, raman spectroscopy and scanning electron microscopy. The structure of the films corresponds to that of bulk crystals of the same composition. Refractive index has been determined by the optical transmission method. Refractive index close to those of bulk crystals are obtained for epitaxially grown zirconia on sapphire substrates, whereas low refractive index values, related with low packing densities, are obtained for thin films in the glassy substrate.     

Raman Studies of ${rm Ti}_{bm{ 1-x}} {rm Fe}_{bm x} {rm O}_{bm 2}$ Nanoparticles

Ti_1-xFe_xO₂ (x = 0.00-0.13) nanoparticle samples were prepared by hydrolysis method. We investigated the effects of Fe doping on the structural and magnetic properties of the Ti_1-xFe_xO₂ nanoparticle system. Scanning electron microscopy and X-ray diffraction measurements confirm that the particle size of the powder is in nanoscale, and that the magnetic Fe impurities substitute for the Ti sites in the anatase TiO₂ phase. All the samples with x > 0 were found to be super-paramagnetic at room temperature by magnetization measurements. Raman spectra also strongly support that the Fe atoms go into the Ti-site in theTiO₂ structure. For comparison, ceramic Ti_1-xFe_xO₂ samples were also prepared by usual ceramic method. Ferromagnetism was observed only in the ceramic Ti_1-xFe_xO₂ system. Additional Raman peak at around 610 cm^-1 is observed only in the ceramic samples. This may be related to the clusters created by mixture of various valence state of Fe, which probably would be the cause for ferromagnetism observed in the ceramic Ti_1-xFe_xO₂ system.     

Structural, dielectric and optical properties of Ba(Ti, Zr)O3 thin films prepared by chemical solution deposition

Ba(Ti_0.95Zr_0.05)O₃ (BTZ) thin films grown on Pt/Ti/SiO₂/Si(100) substrates were prepared by chemical solution deposition. The structure and surface morphology of BTZ thin films has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). At 100 kHz, the dielectric constant and dissipation factor of the BTZ film are 121 and 0.016, respectively. The ellipsometric spectrum of the BTZ thin film annealed at 730 °C was measured in the range of wavelength from 355 to 1700 nm. Assuming a five-layer model (air/surface roughness layer/BTZ/interface layer/Pt) for the BTZ thin films on platinized silicon substrates, the optical constant spectra (refractive index n and the extinction coefficient k) of the BTZ thin films were obtained.     

Epitaxial and polycrystalline BaFe12O19 thin films grown by chemical vapour deposition

Epitaxial and polycrystalline barium hexaferrite BaFe₁₂O₁₉ thin films were prepared by metalorganic chemical vapour deposition (MOCVD). Films were grown by a liquid MOCVD technique which aim is to control precisely the precursor vapour pressures. Two kinds of substrates were used: sapphire (001) and silicon thermally oxidized. On Si/SiO₂ films are polycrystalline and the magnetization is isotropic. On Al₂O₃ (001), structural studies reveal the films to be predominantly single phase, well crystallized without annealing procedure and with the c-axis perpendicular to the film plane; epitaxial relationships between the film and the substrate were determined. The magnetic parameters, deduced from vibrating sample magnetometer measurements, show a high dependence of the magnetization with the orientation of the field with respect to the surface of the film.     

Sc2W3O12薄膜制备及其负热膨胀性能

采用脉冲激光沉积法制备了斜方相Sc₂W₃O₁₂薄膜。利用X射线衍射仪(XRD)和场发射扫描电镜(FESEM)对Sc₂W₃O₁₂靶材和Sc₂W₃O₁₂薄膜组分、表面形貌和靶材断面形貌进行表征, 研究衬底温度与氧分压对薄膜制备的影响。采用变温XRD和热机械分析仪(TMA)分析了Sc₂W₃O₁₂陶瓷靶材和薄膜的负热膨胀特性。实验结果表明: 经1000℃烧结6 h得到结构致密的斜方相Sc₂W₃O₁₂陶瓷靶材, 其在室温到600℃的温度范围内平均热膨胀系数为-5.28×10^-6 K^-1。在室温到500℃衬底温度范围内脉冲激光沉积制备的Sc₂W₃O₁₂薄膜均为非晶态, 随着衬底温度的升高, 薄膜表面光滑程度提高; 随着沉积氧压强增大, 表面平整性变差。非晶膜经1000℃退火处理7 min后得到斜方相Sc₂W₃O₁₂多晶薄膜, 在室温到600℃温度区间内, Sc₂W₃O₁₂薄膜的平均热膨胀系数为-7.17×10^-6 K^-1。     

Ti811合金表面激光熔覆Ti2Ni+TiC+Al2O3+CrxSy复合涂层的组织和性能

以TC4+Ni45+Al₂O₃+MoS₂+Y₂O₃混合粉末为熔覆材料,采用同轴送粉技术在Ti811合金表面进行激光熔覆制备复合涂层,使用SEM、EDS和XRD等手段分析了涂层的微观组织,测试了涂层的显微硬度和摩擦磨损性能。结果表明,在激光熔覆过程中Ti811合金中的Ni和C分别与Ti发生反应,原位生成金属间化合物Ti₂Ni和硬质增强相TiC;MoS₂分解后S与Cr发生硫化反应生成了软质润滑相Cr_xS_y。网状形态的Ti₂Ni、近球状和枝晶形态的TiC以及点状的Al₂O₃,均匀分布在熔覆层中。硬质相强化和软质相润滑的共同作用,使激光熔覆层具有较高的显微硬度和较优良的耐磨性能。激光功率为900 W的熔覆层其平均显微硬度值达1303.5HV_0.5,其耐磨性能最佳。     

Investigation on the cross sensitivity of NO2 sensors based on In2O3 thin films prepared by sol-gel and vacuum thermal evaporation

In₂O₃ thin films have been prepared from commercially available pure In₂O₃ powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500°C for 24 and 1 h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500°C the films’ microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In₂O_3−x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In₂O₃ (HVTE) and nearly stoichiometric In₂O_3−x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO₂ gas (0.7–7 ppm concentration range), at 250°C working temperature. At this temperature and 0.7 ppm NO₂ the calculated sensitivities (S=R_g/R_a) yield S=10 and S=7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In₂O₃ films to CO and CH₄. Negligible H₂O cross has resulted in the 40–80% relative humidity range, as well as to 1 ppm Cl₂ and 10 ppm NO. Only 1000 ppm C₂H₅OH has resulted to have a significant cross to the NO₂ response.     

New LaCu0.5Mn0.5O3 thin films deposited by the sol-gel process on different substrates

New LaCu_0.5Mn_0.5O₃ thin films deposited by the sol-gel process on ceramic Al₂O₃ and ZrO₂, glass ceramic and 101 single-crystal quartz, using the sol-gel process. It was found in all cases that the films are polycrystalline and single phase without preferred orientation. The morphology of the films depends strongly on the nature of the substrate. The films deposited on Al₂O₃ exhibit morphological characteristics making them suitable as possible sensors and catalysts.     

新型Ti_3AlC_2-Al_2O_3/TiAl_3复合材料的组织结构与性能

利用Al-TiO2-TiC体系,通过机械球磨和反应热压制备出Ti3AlC2与Al2O3两相原位内生成增强TiAl3金属基复合材料。借助DSC、XRD、SEM和TEM研究了复合材料的反应机制、显微组织、力学性能及抗氧化性能。结果表明,球磨50h后的复合粉末经1 250℃/50 MPa保温10min烧结后可得到组织均匀细小且致密的Ti3AlC2-Al2O3/TiAl3复合材料,其密度、维氏硬度、室温三点弯曲强度、断裂韧性及压缩强度分别为3.8g/cm3、8.4GPa、658.9 MPa、7.9 MPa·m1/2和1 742.0 MPa,1 000℃的高温压缩强度为604.1 MPa。Ti3AlC2-Al2O3/TiAl3复合材料的增韧机制主要包括Ti3AlC2和Al2O3颗粒的剥离、Ti3AlC2相导致的裂纹偏转和桥接以及Ti3AlC2颗粒的变形及层裂。Ti3AlC2-Al2O3/TiAl3复合材料在700~1 000℃温度区间内生成的氧化层虽不致密,但仍表现出优异的抗高温循环氧化性能。     

-Fe2O3 thin films prepared by metalorganic deposition (MOD) from Fe(III) 2-ethylhexanoate

-Fe₂O₃ thin films were prepared by metalorganic deposition (MOD) using Fe(III) 2-ethylhexanoate as the metalorganic precursor. A series of experiments were conducted on the metalorganic spin-coated films and their correspondingly annealed samples by employing experimental techniques ranging from thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to optical property characterization. In this way a better understanding has been achieved regarding the decomposition process of the metalorganic precursor, the solid state -Fe₂O₃ film formation and crystallization process, and the relationship between the structure and the optical properties of the prepared films. The conclusions of our experiments are the following. The decomposition of Fe(III) 2-ethylhexanoate is a multistep process that is characterized by distinct transition temperatures and thermogravimetric loss rates. Amorphous -Fe₂O₃ film is formed at an annealing temperature of around 460°C, further annealing at higher temperatures induces the amorphous-to-crystalline phase transition and grain growth. FTIR, XRD and SEM data for structural characterization are correlated and in good agreement. A new FTIR absorption band, peaking at 1085 cm^-1, is assigned to the vibration of crystalline Fe-O mode, therefore this peak is useful in monitoring the amorphous-to-crystalline phase transition of -Fe₂O₃ material. Instead of columnar structure in physical vapour deposition-prepared films a granular structure is typical of MOD prepared films, the grain size is much larger near the surface of the film than near the substrate. Optical characterization shows that the refractive index and extinction coefficient of the -Fe₂O₃ thin films increase with the increase of annealing temperatures. The potential interesting applications of the MOD-prepared -Fe₂O₃ thin films include gas sensor materials, photoelectrodes and storage media.     

Chemical analysis of NiAlFe thin films sputter deposited onto sapphire substrates

NiAlFe thin films were prepared onto sapphire single crystals by physical vapour deposition (PVD) and these were analysed by X-ray photoelectron spectroscopy (XPS) in combination with argon ion etching to determine the composition depth profile and interfacial characteristics of the samples. Non-linear least square fitting (NLLSF) analysis of the data was required due to the conflict of several peaks of interest. XPS depth profiles show that, for non-annealed NiAlFe–Al₂O₃, the interface is sharp and oxygen diffusion occurs at different annealing temperatures. Ni remains chemically unaffected by the presence of oxygen while the formation of aluminium oxide compounds occur. Two iron species are present in the film thickness where the low binding energy component is attributed to Fe–Fe or Fe–Al interactions and the higher one to the NiAlFe compound. The reduction-dissolution of the sapphire substrate leads to depletion of oxygen in the sapphire surface layer and the formation of alumina at the NiAlFe–Al₂O₃ interface. Within the film, aluminium and nickel are present as an intermetallic compound. Annealing of the samples induces surface oxidation and the subsequent formation of an Al₂O₃ layer. This type of interphase morphology should lead to optimal fibre/matrix (F–M) adhesion, and therefore optimal load transfer between the matrix and reinforcement.     

陶瓷添加物对Ti_3SiC_2基复合材料抗氧化性的影响

为研究陶瓷添加物对Ti3SiC2基复合材料性能的影响,首先,采用反应热压烧结法制备了Ti3SiC2材料及陶瓷添加物含量均为30wt%的SiC/Ti3SiC2、Al2O3/Ti3SiC2和MgAl2O4/Ti3SiC2复合材料。然后,测试了材料的力学性能和导电性,在1 373~1 773K温度范围内对Ti3SiC2基复合材料的抗氧化性进行了研究,并对其烧结试样的物相组成和显微结构等进行了表征。结果表明:Ti3SiC2在高温氧化后的主要产物为TiO2和SiO2;氧化层分为内外2层,内层由TiO2与SiO2这2相混合组成,外层为TiO2;氧化层中存在大量显气孔,结构较为疏松,导致抗氧化性较差。与Al2O3/Ti3SiC2和MgAl2O4/Ti3SiC2复合材料相比,SiC/Ti3SiC2复合材料具有更好的抗氧化性。     

Yttrium oxide film deposition by a Langmuir-Blodgett processing technique and its incorpiration into oxide scales by substrate oxidation

Thin films (about 10 nm) of Y₂O₃ have been deposited by a Langmuir-Blodgett processing technique onto a variety of substrates: type 304 stainless steel, low carbon steel, titanium, zirconium and silicon. The substrates were afterwards oxidized in air at 800, 1000 (304 steel), 400 (low C steel), 500 (Ti), 450 (Zr) and 1000 (Si) °C. The effects of the film on the oxide scale thickness and the interaction between Y₂O₃ and the oxide of the substrate have been studied by ion backscattering. In stainless steel, the Y₂O₃ film reduces the oxidation rate by orders of magnitude and Y is distributed throughout the oxide scalw (1–10 at.% level). In other substrates, the effect on oxidation rate was less pronounced, but changes in the visual appearance often took place. The Y₂O₃ incorporation varied for the different substrates, and Y₂O₃ remained as a surface film in the cases of Ti and Si. Such films exhibited good adherence and could not be removed by wiping. The potential use of metal oxide thin films for surface analysis standards and diffusion marker studies is discussed.     

Enhancement of the dielectric properties of Pb(La,Ti)O3 thin films fabricated by pulsed laser deposition

PLT thin films with a thickness of 600 nm were grown by pulsed laser deposition (PLD) using different laser wavelengths of 355, 532 and 1064 nm, respectively. We have systematically investigated the variation of grain sizes depending on the process condition. A two-step process to grow (Pb_0.72La_0.28)Ti_0.93O₃ (PLT) films was adopted and verified to be useful to enlarge the grain size of the film and to enhance leakage current characteristics. Structural and electrical properties including dielectric constant, ferroelectric characteristics, and leakage current of PLT thin films were shown to be strongly influenced by grain size.