The influence of grain boundary conductivity and microstructure on the electrical properties of BaCe0.85Gd0.15O3–δ have been examined. Grain sizes were varied by sintering at various temperatures. Impedance data were analyzed using the brick layer model, and some new consequences of this model are presented. The specific grain boundary conductivity exhibits an activation energy of ~0.7 eV, and for similar processing routes, is independent of grain size. An isotope effect was observed, indicating that protons (or deuterons) are the mobile species. TEM investigations showed the intergranular regions to be free of any glassy phase that could account for the differences in bulk and grain boundary properties. Single-crystal fibers, grown by a modified float zone process, were notably barium deficient, and exhibited a low conductivity, comparable to that of polycrystalline Ba0.96Ce0.85Gd0.15O3–δ.

The growth of epitaxial thin films of Li1–xNb1–xWxO3 from solution precursors on single-crystal LiNbO3 substrates is reported. An all-alkoxide solution readily gave single phase powders after simply mixing the constituent components, whereas an acetate-alkoxide system required additional solution processing stages to give phase pure powders. Heat treatment of films on single-crystal, basal plane LiNbO3 substrates at 600 °C formed a nanocrystalline, porous film which was converted to an epitaxial film after heating to 800 °C. Measurements of second harmonic generation in powders indicate an increase in SHG efficiency with increasing tungsten content. Optical absorption data for films were calculated using reflectance and transmittance spectroscopy data, and indicate a decrease in bandgap with increasing tungsten.

This paper outlines the formation of alkaline earth metal titanates, of the general formula MTiO3, directly from the metal oxides and rutile by mechanical activation in a laboratory ball mill at room temperature. X-ray diffraction analysis showed that the reaction was essentially complete within 100 h for all metals except magnesium. The titanates formed all had a Scherrer crystallite size of 11–12 nm and a lattice strain of 0.5–0.6%, neither of which were affected by extended milling. Annealing studies confirmed that the titanate was formed during milling and showed that grain growth could be achieved at temperatures below that generally used for their formation. Mixed cation titanates could also be formed by milling, but tended to be barium rich until annealed.

The preferred orientation, grain morphology, and composition heterogeneity of the polycrystalline Pb(ZrxTi1–x)O3 (PZT) thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and x-ray energy dispersive spectroscopy (EDS). PZT thin films with nominal x = 0.5 were grown by metal-organic chemical vapor deposition (MOCVD) on (110)- and (101)-textured RuO2 bottom electrodes at temperatures ≤525 °C. Columnar grain microstructure with strongly faceted surface morphology was observed in both films. The grain morphology and surface roughness of the PZT films were observed to depend on those of the underlying RuO2 layers. TEM-EDS analysis shows notable cation composition heterogeneity in length scales of 0.2–2 μm. Pronounced Pb composition deficiency and heterogeneity were also observed in PZT/(110)RuO2 in length scales above 40 μm. The grain morphology and cation heterogeneity of the PZT films are discussed on the basis of diffusion-limited columnar growth mechanism.

An interesting reverse burning phenomenon was observed during the combustion synthesis of zirconium-based materials. When an external heat was applied to one end of a green pellet, the ignition was initiated at the other end. Also, the ignition position, measured from the heated end, was proportional to the apparent green density of the compact. The possible explanations for this reverse burning phenomenon are discussed.

Layers of different composition and/or grain size of yttria partially stabilized zirconia (YPSZ) have been compressed, with the stress perpendicular to the interface of the layers and temperature of 1400 °C, in order to produce a joint using the microstructural feature of superplasticity found in fine-grained ceramics. The pieces joined have been characterized by scanning electron microscopy (SEM), showing a clean interface with no cavitation. The stiffness of the junction was checked using Vickers indentation at room temperature at the interface and compression tests at the same conditions (T = 1400 °C in air) used for the joining and the stress parallel to the interface. The observation and comparison between the cracks developed around the indents at the interface and in the bulk of the pieces joined as well as the absence of cavities along the interface in the samples compressed parallel to the interface shows that this technique is useful to produce a joint with a clean and strong interface.

This paper discusses the influence of the synthesis technique on the porous structure, phase transformation, and catalytic properties of barium hexaferrite. Barium hexaferrite was synthesized by two different citrate gel methods. The first one involved metal salts, citric acid, and ammonia, while the second dispersed the same components in a polyacrylamide gel. X-ray diffraction analysis was used to determine the nature of the phase while the Brunauer, Emmett, and Teller (BET) analysis was used to study the porous structure of the material which were heat-treated at 700 °C, 900 °C, and 1200 °C. The catalytic activity of all materials in the combustion of methane was also measured.

The influence of the niobium content on the anatase-to-rutile phase transition in nanopowders of Nb–Ti oxides was studied and the changes in the particle size and microstrain distribution obtained at different temperatures were analyzed. A correlation is found between the initial microstructure in the Ti1 – xNbxO2 (x = 0.03, 0.2) powder and the niobium content. The presence of Nb was found to inhibit the growth of both the anatase and the rutile phases.

A device for spherical indentation using a tip radius of 2 mm and loads up to 10 kN is presented. This facility can be applied, for example, to verify methods for characterizing the behavior of materials exhibiting homogeneous and isotropic constitutive properties. The indentation device can be driven both load- and depth-controlled. The accuracy of measurements is about 1 N for load and 0.2 μm for depth at a total depth of 200 μm. Two materials, an austenitic steel and an aluminum alloy, have been tested and their Young's moduli have been determined. For determining Young's modulus from spherical indentation data, use is made of a so-called Lt method, which had been developed in Ref. 1. Results obtained in this way are compared with corresponding values measured by one-dimensional homogeneous tensile experiments.

Surface hardening by laser irradiation was examined regarding the loss factor, which is the parameter of the vibration-damping characteristics, for flake graphite cast irons and spherical graphite cast irons. The surface of the samples was quenched by changing speed of beam, gas pressure, and beam frequency. It was found that the depth of the hardening region was from 0.12 mm to 1.11 mm, and the hardness of the boundary between the hardening and the nonhardening regions changed suddenly. It was confirmed that the loss factor of the laser hardened specimens increased considerably as compared with that of the as-cast specimens. The internal friction at the vicinity of the boundary between the hardening and the nonhardening regions may be responsible for this result.

A novel precursor solution system, containing NH3 as a complexing agent, was used for the production of Ag powders by spray pyrolysis. Solutions of Ag2CO3, Ag2O, and AgNO3 with NH4HCO3 were used in this study. Ag powders were obtained at unexpectedly low temperatures, i.e., 400 °C or less. The Ag powders with a shell-like morphology were obtained from Ag2CO3 and Ag2O solutions, whereas dense Ag particles of about 1 μm diameter were obtained from AgNO3–NH4HCO3 solution. These morphologies are explained in terms of NH3 release during spray pyrolysis.

Optical quality Al films were evaporated by an electron beam onto Si wafers in an ultrahigh vacuum system. The as-deposited samples were radiative heated at a rate of 3 °C/s in air environment. During heating, measurements of initial hillocking and changes in overall film stress were performed simultaneously and in real time as a function of time and temperature with a specially designed optical instrument. The physical principles of this instrument are based on laser beam deflection caused by film stress induced wafer bending and partial integrated light scattering from surface roughening. The experimental results show how the initial hillocking is accompanied by changes in the overall stress and yield a very good correlation between the onset of hillock formation and the maximum change in overall stress.

A systematic investigation of erbium diffusion in lithium niobate (LiNbO3) crystal as a function of crystal cut-direction, diffusion process parameters (temperature and time), and initial film thickness is reported. Depth concentration profiles of erbium are obtained by secondary ion mass spectrometry (SIMS). Combining experimental data with diffusion theory, the relevant diffusion parameters are derived. Diffusion from an infinite source of erbium ions is studied to evaluate the solid solubility lower limit of Er in LiNbO3. A thin film diffusion regime, with complete depletion of ion source, is also investigated. A comparison of Er diffusion with Er/Ti codiffusion in LiNbO3 crystals is reported.

Small titania particles, prepared by hydrolysis and condensation using in situ steric stabilization, have been studied by high-energy, transmission, electron energy-loss spectroscopy. Electron diffraction patterns and energy-loss spectra as a function of momentum transfer were measured for as-prepared particles (amorphous titania), particles annealed at 600 °C (primarily anatase), and particles annealed at 1000 °C (primarily rutile). The energy-loss spectra at low momentum disagreed with the loss function calculated from optical data (rutile) and disagreed with theory (rutile and anatase). The data was fit by an Elliot-like model for a resonant exciton interacting with a continuum of levels. The translational effective mass of the exciton derived from the fitting was quite large, indicating that it was self-trapped.

In this study zinc sulfide thin films were grown by the successive ionic layer adsorption and reaction (SILAR) technique on (100) GaAs substrates from aqueous precursor solutions. The atomic force microscopy (AFM) method was used to study the growth of the films up to a thickness of 180 nm. The ZnS thin films on (100) GaAs were smooth with an rms roughness of 0.2–1.9 nm depending on the film thickness. After the GaAs surface was covered with ZnS, the growth appeared to be nearly layerwise. In addition, in situ AFM studies were carried out to analyze the dissolution of (100) GaAs in water, which is a process competing with the thin film deposition by the SILAR.

Dilatometer push rods exert uniaxial compressive stresses on powder compacts undergoing sintering. In this study the effect of such stresses on the shrinkage anisotropy behavior of glass powder compacts is considered. A shrinkage anisotropy factor (k), defined by the ratio between axial and radial strain, is used to quantify the anisotropy in cylindrical compacts (k = 1 represents isotropic shrinkage). The available experimental data in the literature indicate that the effect of the applied dilatometer stress is to increase the value of k over that of free sintering conditions. For the small stresses exerted by the dilatometer push rods, it is shown that k is always. 1. The common practice of calculating the sintered density from uniaxial dilatometer data, ignoring the existence of shrinkage anisotropy, is shown to lead to significant errors, even for values of k only slightly different from k = 1.

The effects of dimethylformamide (DMF) on morphology and texture of hematite particles produced from a forced hydrolysis reaction of FeCl3 –HCl solution were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), thermogravimetry and differential thermal analysis (TG-DTA), N2 and H2O adsorption, and zeta potential measurements. The morphology of synthetic hematite particles was concentration dependent; they changed from large sphere with a diameter of ca. 600 nm to diamond-like shape with increasing DMF concentration in the aging solution accompanying a reduction of their size to 80 nm without incorporation of DMF in the particles. This fact was explained by an acceleration of phase transformation from β–FeOOH to hematite with an elevation of the solution pH owing to dimethylamine produced from a hydrolysis of DMF at an elevated temperature. TEM and XRD suggested that the diamond-like hematite particles formed above 6–10 vol% DMF possess a single-crystal nature. Gas adsorption technique revealed that the particles produced above 10 vol% DMF possess a high thermal stability. TG and FTIR indicated that the hematite particles produced with DMF contained small amounts of OH_ ions in the lattice though they provided a single-crystal nature.

Absorption spectra of added Co(II) ions and EPR spectra of both Co(II) and ubiquitous Fe(III) ions in an alkali-borosilicate glass of vycor-type composition are studied both before and after thermal phase separation of the glass as well as in a silica glass derived from the phase-separated glass through vycorization. The results show that although almost all Co(II) ions migrate to the separated alkali-borate phase at the time of phase separation, only the interstitial ions in the case of Fe(III) take part in similar migration. The Fe(III) ions in the substitutional silicon sites, however, remain unaffected. It is also revealed that as a consequence of the process of phase separation a small fraction of the interstitial Fe(III) ions gets converted into substitutional ions leading to a net increase in the concentration of substitutional Fe(III) ions in the glass. Analysis of both absorption and EPR spectra of the Co(II) ions suggests that a change of host of the ion due its migration does not bring about any significant change in its coordination structure, which is typically a distorted tetrahedron both in the parent glass as well as in the phase-separated borate glass.

Asymmetric growth of amorphous layer in a Ni/Zr bilayer, in which a thin disordered interlayer is preset, upon annealing at medium temperatures is observed by molecular-dynamics simulation with an n-body potential. It is shown that the amorphous layer is extended from the interlayer with different speeds toward two opposite directions and that the growth kinetics follows time dependence of t1/2, indicating amorphization upon annealing in the Ni/Zr bilayer is indeed through a diffusion-limited reaction. Besides, two low temperature limits allowing the growth of amorphous layer toward Ni and Zr layers are also obtained.

Metastable face-centered cubic (fcc) solid solutions of Ni1–xAlx and Ni1–xZrx have been prepared in thin-film form using dc planar magnetron sputtering in a UHV system. In both these alloy systems, extended solubilities in the fcc phase and a pronounced (111) texture are observed after sputter deposition. An amorphous phase is found to form in Ni1–xAlx for x ≥ 0.30 and in Ni1–xZrx for x ≥ 0.05. Lattice constants, thermal expansion coefficients, and Debye temperatures were derived from x-ray diffraction measurements. These parameters were also calculated by using ab initio methods in the framework of the local-spin density and coherent potential approximations for the electronic subsystem and the Debye–Grüneisen model for the vibrational properties of the nuclei subsystem. Experiment and theory are compared and discussed.