Structure and ultraviolet emission characteristics of amorphous ZnO films grown on indium tin oxide coated glass substrates by electrophoretic deposition were investigated using Raman spectra and photoluminescence. The Raman spectrum shows a unique resonant multiphonon process within amorphous ZnO films. The photoluminescence spectrum of amorphous ZnO films shows a strong ultraviolet emission while the visible emission is nearly fully quenched. The transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectrum, and infrared spectrum are used to detect the structure of amorphous ZnO powder. The complex water plays an important role in the photoluminescence intensity emission.

The stability of titanium oxide nanotube arrays at elevated temperatures was studied in dry oxygen as well as dry and humid argon environments. The tubes crystallized in the anatase phase at a temperature of about 280 °C irrespective of the ambient. Anatase crystallites formed inside the tube walls and transformed completely to rutile at about 620 °C in dry environments and 570 °C in humid argon. No discernible changes in the dimensions of the tubes were found when the heat treatment was performed in oxygen. However, variations of 10% and 20% in average inner diameter and wall thickness, respectively, were observed when annealing in a dry argon atmosphere at 580 °C for 3 h. Pore shrinkage was even more pronounced in humid argon environments. In all cases the nanotube architecture was found to be stable up to approximately 580 °C, above which oxidation and grain growth in the titanium support disrupted the overlying nanotube array.

Structural, mechanical, and electrical properties were examined for C60 whiskers, high-pressure sintered C60 whiskers, and C60 powder. A high density of dislocations was observed in the C60 whiskers, and the C60 whiskers with diameters of a few hundred nanometers were found to be flexible. Although both the specimens sintered under the same condition showed similar surface x-ray diffraction profiles with a strong accumulation of [110]tr orientation, the sintered C60 whiskers showed a higher micro-Vickers hardness and an electrical resistivity four orders of magnitude lower than that of the sintered C60 powder.

Structural properties of polycrystalline Pb(Zr0.35Ti0.65)O3 (PZT) thin films grown by metalorganic chemical vapor deposition on Ir bottom electrodes were investigated. Symmetric x-ray diffraction measurements showed that as-deposited 1500 íthick PZT films are partially tetragonal and partially rhombohedral. Cross-section scanning electron microscopy showed that these films have a polycrystalline columnar microstructure with grains extending through the thickness of the film. X-ray depth profiling using the grazing-incidence asymmetric Bragg scattering geometry suggests that each grain has a bilayer structure consisting of a near-surface region in the etragonal phase and the region at the bottom electrode interface in the rhombohedral hase. The required compatibility between the tetragonal and rhombohedral phases in he proposed layered structure of the 1500 Å PZT can explain the peak shifts observed n the symmetric x-ray diffraction results of thicker PZT films.

Iron-nickel-based powders and thin films were synthesized by an electroless polyol method. The growth process as a function of deposition time was studied. The Fe concentration of deposited films and precipitated powders were similar and independent of deposition time. The metalorganic intermediates were present in powders and their amount decreased with time. The morphological investigations suggested that 60 min was the optimum deposition time to deposit dense films with particles of narrow size distribution. In addition, the films deposited at 60 min also possessed the highest saturation magnetization due to a more ordered atomic environment of nickel. The as-deposited Fe was apparently oxidized in the films.

For this paper, we used radio-frequency (rf) sputter deposition to synthesize epitaxial La0.5Sr0.5CoO3−∂ (LSCO) films. We investigated the influence of sputter deposition parameters, in particular, oxygen partial pressure, plasma power, total sputter pressure, and post-deposition cooling atmosphere on film composition, microstructure, and electrical resistivity. We show that rf sputtering from a single target can produce LSCO films with La/Sr and (La + Sr)/Co ratios of unity and with low electrical resistivities of about 1 mΩ cm. Film microstructures were characterized by high-resolution transmission electron microscopy and x-ray diffraction. Formation of an ordered film superlattice, most likely due to oxygen vacancy ordering, was observed. In this paper, we discuss the relationship between the film microstructure and the electrical resistivity.

Transmission electron microscopy (TEM) was used to investigate the structural properties of sputter-deposited yttria-stabilized zirconia (YSZ) thin films. YSZ films were deposited over a range of temperatures and background oxygen levels. Additionally, a multilayered structure was produced by cyclic application of a substrate bias. Plan-view TEM showed that temperature and oxygen levels did not have a significant effect on grain size but did alter the phases present in the thin films. Cross-sectional TEM showed the development of texture in the multilayer film, both within the individual layers and in the entire film.

Preparation of dense and phase-pure Ba2Ti9O20 is generally difficult to achieve using solid-state reaction, since there are several thermodynamically stable compounds in the vicinity of the desired composition. This study investigated the effects of B2O3 on the densification, microstructural evolution, and phase stability of Ba2Ti9O20. Samples from the host material (2BaO · 9TiO2) with and without the addition of 5 wt% B2O3 were prepared through different processing routes. For the pure host material sintered at temperatures ranging from 800 to 1100 °C, the reaction products followed the sequence of BaTi2O5 → BaTi4O9 → BaTi5O11 → Ba2Ti9O20. The phase transformation proceeded faster in the bulk compared to the free surface of the sample. BaTi5O11 and BaTi4O9 with a minor amount of Ba2Ti9O20 were found in the ground powder of ceramics sintered at 1100 °C. For the samples prepared from host material with the addition of 5 wt% B2O3, Ba2Ti9O20 started to form at temperatures as low as 800 °C. The sequence of reaction products followed Ba4Ti13O30 → BaTi4O9 → BaTi5O11 → Ba2Ti9O20. Sintering at above 1000 °C yielded pure Ba2Ti9O20 phase, suggesting the effective role of B2O3 on the phase stability of Ba2Ti9O20. It was found that precalcination of host material before the addition of B2O3 gives an additional benefit to the Ba2Ti9O20 formation. Crystallization of pure Ba2Ti9O20 phase was completed at a sintering temperature as low as 900 °C without any solid solution additive such as SnO2 or ZrO2, due to the fact that the phase transformation of the samples began with BaTi4O9 and BaTi5O11 during sintering. Also, B2O3 was found to be unstable during the high-temperature sintering at 1200 °C, and the results are discussed.

Two sol-gel derived zirconia powders were prepared at pH = 0.5 and pH = 5.5. They were investigated as a function of temperature using mainly perturbed angular correlation spectroscopy. The aim was to elucidate the relationship between the nanoscopic configurations around Zr4+ ions and the morphology and structure of the powders. The highly porous material resulting from the solution at higher pH could be described mainly by defective and disordered, very hydrolyzed tetragonal arrays. As temperature increased, the amount of these arrays decreased while they became increasingly asymmetric, thus suggesting their superficial localization. The easy removal of hydroxyls led to the early appearance of the monoclinic phase. The gel obtained from the precursor at pH = 0.5 was entirely described by configurations still involving organic residues. After their calcination, the powder underwent a well-defined two-step hydroxyl removal thermal process leading to the crystallization of the tetragonal and the monoclinic phases. The thermal stability of the metastable tetragonal phase in the investigated powders seems to be controlled by their different capability to absorb oxygen.

This paper gives results demonstrating the production of nanoporous platinum through the de-alloying of Cu0.75Pt0.25 alloy in 1 M H2SO4. Both field emission scanning electron microscopy and small angle neutron scattering confirm the presence of porosity with a diameter of approximately 3.4 nm. This is the smallest porosity quantitatively reported from a de-alloying process to date. The small size is attributed to the extremely small values of surface diffusivity expected for Pt at room temperature, effectively eliminating room-temperature coarsening processes. The results also show that larger length scales can be achieved through coarsening at elevated temperatures. The ease of production of porous platinum makes it attractive for possible applications, such as high surface area electrodes for biomedical devices or as catalyst materials.

The role of a compliant adhesive interlayer in determining critical conditions for radial fracture at the undersurfaces of brittle coatings bonded to substrates of dissimilar materials is investigated. Semi-empirical relations for the critical loads are derived by treating the adhesive as part of an effective substrate, thereby reducing the problem to that of a bilayer. A finite-element analysis of a model silicon/epoxy/glass system is used to evaluate adjustable parameters in the analytical relations. In situ experimental observations of crack initiation on the same material system are used to verify these relations. The critical loads depend sensitively on the adhesive thickness and modulus. Delamination at the interface in poorly bonded specimens greatly reduces the critical loads. This analysis affords a basis for predicting the prospective fracture resistance of brittle coatings joined by adhesives.

Electroceramics are used in a variety of applications such as sensors, actuators, capacitors, and varistors. In these applications, the ceramic microstructure often consists of equiaxed, randomly oriented grains. Ferroelectric transducers require poling to obtain useful piezoelectric properties. Poling is difficult for some ferroelectric ceramics because the symmetry-related orientations available for the spontaneous polarization are limited.