Processing and microstructure of porous and dense PZT thick films on Al2O3

The processing of porous PZT thick-film ceramics on Al₂O₃ has been studied. The films were screen-printed from a thixotropic ink of PZT with a 58% solids content. The thick films were sintered between 1000 and 1150°C for 2 h. The sintered films show a 10 m thickness and an average pore diameter ranging from 1–2 m. The PZT forms a continuous skeleton that can be filled with the desired polymer. Dense and continuous PZT films were fabricated by screen-printing PZT ink on previously electroded Al₂O₃ substrates with Ag/Pd 70/30 paste. Densification of the PZT was obtained by sintering near the liquidus temperature of the Ag-Pd system.     

Al/Al2O3多层膜的研究

用真空蒸镀及自然氧化方法在玻璃基底上制备纳米量级的4、5、6、7对层的Al／Al2O3多层膜。采用称重法测定薄膜的厚度；在常温和低温下使用三点法测定多层膜的电特性；用扫描电镜（sEM）观察薄膜的表面和截面的形貌及成分。结果表明：制备的是纳米量级非晶态的Al／Al2O3多层膜，在常温和低温（77K）下均具有类似负阻的特性。     

Catalysis on oriented ultrathin films of platinum on Al2O3

The selectivity of the hydrogenolysis of methylcyclopentane on model thin film catalysts was investigated and the morphology of the particles was checked in parallel by transmission electron microscopy and transmission electron diffraction. The catalysts were island-stage platinum films of defined orientation obtained by evaporating platinum onto (100)- and (111)-oriented NaCl substrates, backing with Al₂O₃ and dissolving the substrate.The catalysts were quite inactive as long as the single-crystal surface was unchanged, and any increase in activity was accompanied by a change in morphology. The results are compared with those obtained on non-oriented films as well as on bulk single-crystal surfaces.     

Surface structure of silver thin films on In2O3:Sn and Al2O 3 †

Surface structure of thin silver films (200 Å) on two technologically important films, indium tin oxide (ITO) and aluminium oxide, has been studied using scanning tunneling microscope. ITO films were prepared by reactive electron beam evaporation. Aluminium oxide films were prepared by oxidizing 2000 Å thick aluminium films evaporated on to H₂ terminated single crystal silicon substrates. The surface structure of silver on ITO and aluminium oxide appeared to be same and was characteristic of Stranski-Krastanov type. The observed asymmetry in the island shape was attributed to the anisotropic nature of the strain fields surrounding the nucleation centres.     

掺Er-Al2O3薄膜发光特性的研究

通过离子束辅助沉积(IBAD)在热氧化SiO2上沉积Al2O3薄膜,在120keV下注入5×10115cm-2Er离子,Ar气氛下773～1273K退火1h.低温下测试PL谱线,随退火温度升高,发光强度上升.973K退火下发光强度特别低,并观察到Si衬底的1140nm峰.光透射谱表明几乎在所有的测试范围内尤其在1530nm处973K退火样品的透射谱强度最强,波导损耗最低.1530nm发光强度随退火温度的变化跟发光强度的变化相反.说明Er离子在514.5nm泵谱吸收界面σ跟Al2O3的光吸收损耗有一定关系.     

Effect of grain size on the electrical and magnetic properties of MgB2 thick films deposited on the Al2O3 single crystal substrates

MgB₂ films having thicknesses of approximately 10 μm have been prepared on the Al₂O₃ single crystal substrates by using ultrasonic spray pyrolysis technique. The films fabricated were then analyzed by means of microstructural, structural, transport and magnetic properties. The influence of grain size, depending on the ex-situ and in situ heating, were investigated. The results obtained showed that the size of MgB₂ grains has an effect on the transport and magnetic properties of the films. Films prepared with in situ heating have small particle size (<50 nm) and were found to be much better properties than the films prepared ex-situ heating, which have larger grains (~1 μm). The best T _c value and critical current density, J _c ^mag , were obtained to be ~36 K and 9.88 × 10⁵ A cm^?2 respectively for the films prepared with small grains. The results were showed that the smaller grain size and in situ heating cycles are essential points for quality thick film MgB₂ fabrication.     

Plasma spraying of Al2O3 and Al2O3Y2O3

A microstructural study has been carried out of plasma-sprayed Al₂O₃ and mixed and sintered Al₂O₃Y₂O₃. In order to ascertain the degree of metastability achieved by plasma spraying, these results are compared with a similar experiment utilizing a CO₂ laser for melting and the hammer-and-anvil technique for quenching of the same materials. X-ray diffraction methods were used to determine the obtained phases and crystal structures. In addition, transmission electron microscopy was used to confirm the phases present and to study their morpology. The porosity was studied with both mercury intrusion porosimetry and small angle neutron scattering. The addition of Y₂O₃ is shown to decrease the porosity from 15% to 7.5%. Adhesion is likewise related to the addition of Y₂O₃ and it is seen that adhesion of the mixture is measurably improved over that of pure Al₂O₃. The implication of these results is discussed.     

KH550修饰Al_2O_3及其对PI/Al_2O_3薄膜性能的影响

通过调整KH550的含量对Al2O3粉体表面进行改性,并用红外光谱(FT-IR)和X射线衍射(XRD)对改性后的粉体进行表征,表征结果显示KH550成功的键合到Al2O3粉体表面。然后分别使用Al2O3以及改性Al2O3制备了一系列无机粉体含量为16%(质量分数)的PI复合薄膜,通过扫描电子显微镜(SEM)对复合薄膜的断面微观形貌进行表征,并对复合薄膜的力学性能和击穿场强进行测试。测试结果显示KH550的含量对无机粉体分散情况有较大影响。当KH550含量为2%(质量分数)时,PI/KH550-Al2O3复合薄膜的拉伸强度和断裂伸长率最优,分别为130 MPa,12%,与PI/Al2O3薄膜相比,拉伸强度和断裂伸长率分别提高了22.8%,44.5%,击穿场强与其相近。     

Shrunk lattice structure and interdiffusion characteristics of 5 nm thick Al(2)O(3) ultrathin films sputtered on silicon

We report that a 5?nm thick Al(2)O(3) film grown on Si(100) directly by sputtering exhibits strong (110) texture, accompanied by a shrunk lattice structure (Δd/d～-2.36%). The disordered nature of the film was confirmed by cross-sectional high-resolution transmission electron microscopy, implying the loosened microstructure responsible for enhanced interdiffusion. The oxygen-deficient Al(2+δ)O(3-δ)(δ>0) interdiffusion region with complex interfacial chemical valences was formed between the Al(2)O(3) film and Si substrate, reducing the insulator properties. Using depth profiling in situ x-ray photoemission spectroscopy, we quantitatively reveal the non-stoichiometry deviation of the Al/O ratio at the interdiffusion region. A nominal thickness of 5?nm is required to obtain an actual barrier thickness of approximately 1?nm.     

Characterization of Al2O3 films deposited by various methods

A comparative study of electron emission characteristics was made for thin films of Al₂O₃ deposited by the techniques of r.f. sputtering, chemical vapour desposition and post-oxidation of vacuum-evaporated aluminum films. A single pusle method was used with a retarding field analyzer for measurement of the yield in secondary electron emission. Relative work functions were determined with respect to gold by a diode gun assembly and the retarding potential method. All measurements were made in an ultrahigh vacuum system. X-ray photoelectron spectroscopy and scanning electron microscopy were used for comparison of the stoichiometry and morphology of the films, and the relative effects of these characteristics on the emission were assessed.The emission characteristics were analyzed semi-empirically by making use of Dionne's theory for secondary electron emission. On the basis of the experimental results, the use of these films in continuing dynodes (for electron multipliers) is proposed. The r.f. sputtered films were found to be the most suitable electron emissive layers.     

Characterization of Al2O3–304 stainless steel braze joint interface

Sintered Al₂O₃ is brazed with 304 stainless steel (SS) using 97(Ag28Cu)3Ti active filler alloy (AFA) at 1000 °C. Interfaces have been systematically characterized by Electron Probe Micro Analysis (EPMA) and Transmission Electron Microscope fitted with Energy Dispersive X-ray (TEM-EDX). The interface thicknesses have been measured from the EPMA concentration penetration profile. The presence of TiO, Cu₃Ti₃O phases in the Al₂O₃ interface and FeTi phase in the SS interface have been confirmed by TEM. Shear strength of the interfaces have been evaluated.     

Al_2O_3:Ce~(3+)薄膜发光特性研究

用中频反应磁控溅射技术制备了Al2O3:Ce3+的非晶薄膜。这些薄膜的光致发光峰是在370～395 nm之间,它来自于Ce3+离子的5d1激发态向基态4f1的两个劈裂能级的跃迁。发光强度依赖于薄膜的掺杂浓度,并分析了产生这种关系的原因。Al2O3:Ce3+非晶薄膜发光特性在平板显示等领域有着广泛潜在的应用前景。     

316L不锈钢基体上反应溅射添加YOx粘接层的Y2O3/Er2O3复合涂层的研究

为了研究添加粘接层对复合涂层的影响,采用脉冲反应溅射在316L不锈钢基体上制备了调制周期为700 nm左右(5层)的Y2O3/Er2O3复合涂层,通过调整氧氩比制备了不饱和氧化钇(YOx,x＜1.5)作为粘接层,研究了添加粘接层对复合涂层相组成、组织形貌以及涂层与基底结合情况的影响.X射线衍射(XRD)、扫描电子显微镜(SEM)、结合力及纳米硬度分析结果表明,当氧分压为0.036 Pa制备YO1.401粘接层时,Y2O3/Er2O3/YOx涂层的结合力相比于Y2O3/Er2O3复合涂层,涂层与基体的结合力增大了约60％,纳米硬度增大了近30％,绝缘电阻率测试结果表明,Y2O3/Er2O3/YOx涂层绝缘电阻率在1×109Ω·cm～1×1011Ω ·cm,绝缘性能良好.     

Slip casting of Al2O3 and Al2O3/ZrO2 composites

Al₂O₃ and Al₂O₃/ZrO₂ composites have been fabricated by slip casting from aqueous suspensions. The physical and structural characteristics of the starting powders, composition of the suspensions, casting behaviour, microstructure of the green and fired bodies and the mechanical properties of the products were investigated. The addition of ZrO₂ to Al₂O₃ leads to a significant increase in fracture toughness when ZrO₂ particles are retained in the tetragonal form (transformation-toughening mechanism) but when microcracking (due to the spontaneous transformation of ZrO₂ from the tetragonal phase to the monoclinic one) is dominant, an excellent toughness value is accompanied by a drastic drop in strength and hardness.