Methods for synthesizing ceramic materials from aqueous solutions at ordinary temperature and pressure are advantageous because of the applicability to making films with wide areas and/or complicated shapes with no requirement of vacuum or high temperature, and because of lower cost. Powder of ZrO2 or LnMeO3 (Ln = La, Nd; Me = Cr, Mn, Fe, Co) perovskite was dissolved in hydrofluoric acid and a solution of fluoro-complex ions was obtained. Boric acid was added to the solution, the fluoride ions were consumed by the formation of BF4-, and then the fluoro-complex ions were hydrolyzed to ZrO2 or LnMeO3 in order to increase the amount of fluoride ions. A number of synthesized particles of ZrO2 or LnMeO3 were observed on the substrates in scanning electron microscope images.

Alumina powders were synthesized by the emulsion combustion method, using w/o (water in oil) type emulsions with different aqueous microsphere sizes. The effects of microsphere size on the size and shape of the synthesized powder were evaluated. The powders were spherical and hollow in shape with a very thin shell (from 10 to 20 nm in thickness) when synthesized from large aqueous microspheres (from 200 nm to 1 μm). The sizes and specific surface areas of the powders were consistent with those calculated. Large particles, which did not correspond to the microsphere size, were obtained from small aqueous microspheres (6 nm). The short distance (7 nm) between microspheres causes the adhesion of particles during the firing process.

Dewetting of eutectic SnPb on blank Au(500 Å)/Cu(1 μm)/Cr(800 Å) layered structure was found to have a solder size dependence. At 250 °C, if the solder weight fell below 4 mg, dewetting occurred from the center of the solder cap; if the solder weight went beyond 6 mg, dewetting happened from the cap edge. In the latter case, a smaller cap with a higher wetting angle was formed at the center and a ring of solder was left around the edge. Large voids were left in the solder cap after dewetting in both cases. In contrast, all solder caps were found to dewet from the edge on a patterned film at 250 °C if the solder ball was large enough to wet the whole film initially, irrespective of the solder size. For comparison, pure Sn, eutectic SnAg, and eutectic SnBi caps also dewetted from the edge of the Au/Cu/Cr thin film, irrespective of the solder size or whether the substrate was patterned. Since eutectic SnPb on blank Au/Cu/Cr is the only case in which a large sideband growth was found and the dewetting occurred from the center, we postulated sideband to be the main factor which controls the unusual dewetting. The link between them is discussed.

Microwave dielectric properties and the relationship between the temperature coefficient of the dielectric constant (τ ɛ) and the tolerance factor were investigated in (Sr0.2Ca0.8) (Ti1–xZrx)O3 ceramics. The τɛ increased linearly as the tolerance factor decreased from 0.984 to 0.929 in the whole composition range of the (Sr0.2Ca0.8) (Ti1–xZrx)O3 solid solution. At the composition of (Sr0.2Ca0.8) (Ti0.04Zr0.96)O3, the dielectric constant was 34 and Q · f was 10,938 GHz and the temperature coefficient of the resonance frequency (τɛ) was supposed to be near zero.

Lead-based relaxor ferroelectric multilayer ceramic capacitors (MLC's) were placed in 0.05 M NaOH solution to evolve hydrogen on their silver termination electrode by electrolysis of water. After this treatment, the MLC's failed as their insulation resistance was greatly decreased, their dielectric loss was considerably increased, and their capacitance was obviously decreased. By annealing in air at 650 °C for 30 min, the properties of the MLC's were restored. It is proposed that electrochemically generated hydrogen atoms can diffuse into the ceramic body of MLC's and undergo reduction to it, which may be one of the reasons for the negative influence of electroplating on lead-based relaxor ferroelectric MLC's.

The stibiotantalite (ABO4) family includes a number of ferroelectrics and antiferroelectrics with excellent potential for applications. We report the deposition of phase-pure, polycrystalline thin films of BiNbO4 on Si(100) substrates using pulsed laser ablation. The deposition conditions were optimized with respect to substrate temperature, laser parameters, and the ambient oxygen pressure. The films were characterized by x-ray diffraction, energy dispersive x-ray analysis, and Raman spectroscopy, while their microstructure was studied by atomic force microscopy and scanning electron microscopy. Dielectric hysteresis studies indicated that films with a thickness below ≈250 nm are ferroelectric, while thicker ones are antiferroelectric.

Errors are noted in two publications on the theory for Mirage-effect measurements of the thermal diffusivity of materials. The works include theory for interpreting Mirage experiments on homogeneous samples mounted on a support with ambient (typically air) above and theory for interpreting Mirage experiments on coated substrates with ambient both above and below.

The growth of coalesced, highly oriented diamond films has been achieved on nickel substrates using a multistep process that consisted of (i) seeding the Ni surface with 0.5 μm diamond powder, (ii) annealing at 1100 °C in a hydrogen atmosphere, and (iii) growth at 900 °C in a mixture of hydrogen and 0.5% methane. Auger depth profile analysis of a sample quenched after the annealing stage showed the presence of significant amounts of carbon (6 at. %) close to the substrate surface and about 3 at.% deeper in the substrate. The loss of carbon into the substrate resulted in relatively low nucleation density. The addition of methane into the gas phase during the annealing stage proved very effective in compensating for the diffusion. An addition of 0.5% methane in the gas phase produced optimum results, as the nucleation density, orientation of diamond particles, and uniformity were substantially improved. Substrates nucleated under these conditions were grown out into coalesced, 30 μm thick films. Both (100) and (111) oriented films showed a high degree of orientation and Raman spectra obtained from these orientations showed intense and narrow diamond signature peaks with FWHM's of 5 and 8 cm-1, respectively.

Structural and bonding characteristics of simplified (Pd, Te) precipitates have been determined in a simulated nuclear French glass using extended x-ray absorption fine structure (EXAFS) and x-ray diffraction. In this sample, these precipitates have a homogeneous composition, with about 10 wt.% Te. They retain a face-centered cubic structure as in pure Pd with a cell parameter which obeys Vegard's law. Pd K-edge EXAFS shows the presence of Te in the Pd coordination shell, with (Pd–Te) distances of 2.80 Å. These distances, higher by 0.05 Å than the (Pd–Pd) distances, may result in a lower packing efficiency of the CFC lattice. The comparison with the average distances derived from x-ray diffraction shows the nonmetallic character of the Pd–Te bond in these precipitates. These bonding modifications may cause the limited solubility of Te in metallic Pd.

Optical studies have been performed on amorphous films of the system Ge10Se90-xTex where (x = 20, 30, 40). The study revealed that as the Te content is increased, the optical band gap (Eg) was found to decrease. Photoinduced effects were studied on thin films samples irradiated with either white light or uv light. The shift in Eg due to photoirradiation disappears upon annealing the films at a temperature below the glass transition temperature. The effect of γ-radiation up to 8 kGy on the optical band gap was also investigated, and no detectable shift of the optical band gap was observed. The relationship between the optical band gap and both the average heat of atomization and the average coordination number of the compositions under investigation was studied.

The plume generated by ablation of hydroxyapatite targets under ArF excimer laser irradiation has been investigated by means of fast intensified charge coupled device (CCD) imaging and optical emission spectroscopy. Results have shown that the plume splits into two plasma clouds as it expands. Time and spatial resolved spectra have revealed that under the experiment conditions emission is mostly due to calcium neutral atoms and calcium oxide molecular radicals. Imaging of the plume with the aid of bandpass filters has demonstrated that the emissive species in the larger and faster plasma cloud are calcium neutral atoms whereas in the smaller and slower one are calcium oxide molecular radicals.

The structure model for HgTlBa2CuOx was proposed from high-resolution electron microscopy using residual indices. Averaged digital high-resolution image of the HgTlBa2CuOx showed the existence of separated Hg layers and oxygen vacancies in the double (Hg, Tl) layers. Image calculations based on the proposed structure model of HgTlBa2CuO5 agreed well with the observation, and showed low residual values. The present result indicates the stability of the (Hg, Tl) double layer structure would be due to the formation of oxygen vacancies in the Hg layers.

The characteristic platelet-like structure of large grain superconducting Y–Ba–Cu–O fabricated using peritectic solidification techniques has been documented widely as a key microstructural feature of this material. The platelet formation mechanism is investigated via a detailed comparison of the difference in morphology of YBa2Cu3O7–δ (123) growth fronts propagating along different lattice directions. The development of YBa2Cu3O7–δ dendrites between the growth front and local Y2BaCuO5 (211) particles is observed to be a key feature of the growth mechanism along all directions. Dendrites broaden rapidly for growth fronts propagating along the c-axis due to the enhanced growth rate of Y–Ba–Cu–O in the a-b plane to yield a uniform, regular growth morphology. Dendrite broadening is inhibited for grain growth along the a-b directions, however, due to the slower growth rate along the c-axis, which yields an irregular extended growth front. Growth along the a/b direction commonly results in the formation of regions consisting of 123 dendrites which may connect 211 particles. Continued solidification of the 123 phase in such regions results in the development of platelet structures perpendicular to the crystallographic c-axis in the YBa2Cu3O7–δ phase matrix which may impede the flow of current through the grain in the superconducting state.

Definitive evidence on the variable degrees of order/disorder in the layered perovskite La2Ba2Cu2Ti2O11 is presented. This oxide was prepared by the ceramic method with varying reaction times and cooling rates; the average and local structures of the resulting solids were studied by x-ray diffraction, electron diffraction, and transmission electron microscopy (low and high resolution). The data clearly show the presence of an ap × ap × 4ap layered perovskite superstructure with a high concentration of defects in samples prepared over 48 h but with increasing degree of order for samples with longer reaction times. For samples reacted over 17 days, the order is complete and identical to that found for other related derivatives such as Ln2Ba2Cu2Ti2O11 (Ln = Nd, Eu, Tb). This behavior clearly indicates the existence of a kinetic control of order in this phase.

Zinc oxide varistors are very complex systems, and the dominant mechanism of voltage barrier formation in these systems has not been well established. Yet the MNDO quantum mechanical theoretical calculation was used in this work to determine the most probable defect type at the surface of a ZnO cluster. The proposed model represents well the semiconducting nature as well as the defects at the ZnO bulk and surface. The model also shows that the main adsorption species that provide stability at the ZnO surface are O-, O2-, and O2.

Highly (111) oriented Cu films with a thickness around 1800 Å were prepared on Si(100) at room temperature by partially ionized beam deposition (PIBD) at pressure of 8 × 10-7-1 × 10-6 Torr. Effects of acceleration voltage (Va) between 0 and 4 kV on such properties as crystallinity, surface roughness, resistivity, etc. of the films have been investigated. The Cu films deposited by PIBD had only (111) and (200) planes, and the relative intensity ratio, I(111)/I(200) of the Cu films increased from 6.8 at Va = 0 kV to 37 at Va = 4 kV. There was no indication of impurities in the system from Auger electron spectroscopy (AES) analyses. A large increase in grain size of the films occurred with Va up to Va = 1 kV, but little increase occurred with Va > 1 kV. Surface roughness of the Cu films decreased with Va, and resistivity showed the same trends as that of the surface roughness. In the Cu films by PIBD, it is considered that changes of resistivity are mainly due to a surface scattering rather than a grain boundary scattering. The via holes, dimensions of which are 0.5 μm in diameter and 1.5 μm in depth, in the Cu films made at Va = 4 kV were completely filled without voids. Interface adhesion of the Cu film on Si(100) deposited at Va = 3 kV was five times greater than that of Cu film deposited at Va = 0 kV, as determined by a scratch test.

The structural and electrochemical properties of the Ti–Ru–Fe–O system have been studied over the whole ternary metal compositional range, keeping constant the oxygen content at 30 at.%. The phase diagram was explored systematically by varying the composition of the material along one of the following axes: (i) constant Ru content of 16 at. %; (ii) constant Ti/Ru ratio of 2; (iii) constant Ti/Fe ratio of 1.6. For O/Ti ratios equal or below unity, the most prominent peaks observed in the x-ray diffraction patterns belong to a B2 structure. For O/Ti ratio larger than unity, stable titanium oxide phases are formed, which coexist with a cubic Fe-like or hcp-Ru like phases depending on the Fe/Ru ratio. Powder compositions with stoichiometry close to Ti2RuFeO2 are of interest due to good electrocatalytic properties, long-term stability, and low Ru content.

Homogeneous or uniform crystalline materials are obtained following the ball milling of pure elemental powders of Fe and Zn in proportions to yield single phases Γ(Fe3Zn10), Γ1(Fe5Zn21), and Γ + Γ1 mixed phase (Fe25Zn75). Differential scanning calorimetry (DSC) measurements of the as-milled materials show characteristic stages in the temperature range of 50–600 °C prior to establishing stable equilibrium. The activation energies determined from kinetic analyses range from 49 to 189 kJ/mole in these materials. A characteristic stage at 130 °C marking the distinct evolution of the Γ and Γ1 phases from the intermediate or mixed phase composition is identified from XRD measurements. The identification of a unique Fe site with a quadrupole splitting (QS) of 1.5 mm/s in corroboration with x-ray diffraction (XRD) shows that this stage marks the onset of an in situ transformation prior to the distinct evolution of the homogeneous phases. The Mössbauer effect measurement of the as-milled materials are resolved in terms of four unique Fe sites with QS of 1.1, 0.241, 0.073, and 0.0772 mm/s.

Pulsed electrodeposition is a simple, yet versatile method for the production of nanostructured metals. For n-nickel we determine the influence of the physical and chemical deposition parameters on the nanostructure of the deposits and demonstrate that the grain size can be tuned to values between 13 and 93 nm, with rather narrow grain size distribution. The thermal stability of our n-nickel as studied by x-ray diffraction and differential thermal analysis exhibits no detectable grain growth up to temperatures of about 380 K and an initial behavior at 503 K followed by a regime of anomalous grain growth. For nanocrystalline Ni1-x Cux (Monel-metal™) we demonstrate that alloy formation occurs at room temperature and that both chemical composition and grain size can be controlled by the pulse parameters and by appropriate organic additives.

Formation of nanocrystalline Al3Ti, TiAl, Ti3Al, and Ti5Si3 composites by mechanically alloying (MA) in the Ti–Al–Si system and subsequent annealing treatment are investigated. Microstructure development was monitored by x-ray diffraction, differential thermal analysis, and transmission electron microscopy. An amorphous phase could be generated through milling for 100 h. The results of annealing at different temperatures on this amorphous phase show that the formation of titanium aluminides (Al3Ti, TiAl, and Ti3Al, according to the initial relative amount of Ti and Al) and Ti5Si3 (the only silicide produced by the crystallization reaction) take place. Annealing produces nanocrystalline composites of Al3Ti, TiAl, Ti3Al, and Ti5Si3 with a grain size less than 20 nm. With increasing annealing temperature, the crystalline sizes of the phases increased.