The hydrothermal growth of perovskite BaTiO3 powders has been studied by transmission electron microscopy. The growth is carried out under high alkaline conditions (pH — 14) achieved with Ba(OH)2. Anatase (TiO2) is used as a titanium source. The perovskite BaTiO3 nucleates heterogeneously on anatase TiO2 particles with an epitaxial relationship of (001)TiO2 ‖ (001)BaTiO3 and [010]TiO2 ‖ [010]BaTiO3. This epitaxial relationship preserves the parallel alignment of the oxygen octahedra between the structures. A mosaic misorientation between (001)TiO2 and (001)BaTiO3 along 〈110〉 is seen in this relationship due to the lattice mismatch between TiO2 and BaTiO3. After complete conversion of the anatase to BaTiO3, the BaTiO3 particles develop into {111} octahedrons with ∼10 nm {001} and {110} microfacets on the {111} faces. This evolution suggests that {111} becomes the stable crystallographic facet for BaTiO3 under highly alkaline conditions.

Dislocations in the misfit epitaxial film system In0.25Ga0.75As on GaAs(001) were imaged using a modified electron channeling contrast technique in a LaB6 SEM. We obtained images at an incident beam energy of 30 keV, a beam divergence of less than 1 mrad and a specimen tilt of 70° in conjunction with a movable scintillator detector mounted at a takeoff angle of approximately 3° to 5°. We achieved a spatial resolution of approximately 80 to 100 nm with this technique. Such resolution allowed rapid imaging of clusters consisting of only a few closely spaced dislocations in a 55 nm thick film. At such small film thicknesses, we did not require accurate knowledge of the incident beam direction in order to obtain sufficiently strong channeling contrast for qualitative characterization. The observed defect arrangements included features that we believe represent clustered threading segments.

Macrosegregation of Y2Ba1Cu1O5 (Y211) particles was observed in Pt-added Y1Ba2Cu3O7−δ (Y123) crystals grown by an undercooling method. It was found that the macrosegregation of Y211 particles depended on the growth direction and the growth rate (R) as a function of undercooling (ΔT). The amount of Y211 particles in Y123 crystals grown at large R was larger than at small R. Also, the amount of Y211 in Y123 growing along the a-direction was larger than that along the c-direction. Further, it was noted that the smaller Y211 particles in size were distributed in Y123 grown at large R. These phenomena could be at least qualitatively explained by the prevalent trapping/pushing theory. In the direct observation of magnetic flux with the Faraday effect of iron garnet film, the flux pinning force was found to be in good agreement with the macrosegregation of Y211 particles.

The molten salt method has in the past been employed to synthesize a large number of compounds at low temperatures. In this work we report the formation of solid solutions of BaTiO3–SrTiO3 and BaZrO3–SrZrO3 using a molten salt eutectic of NaOH–KOH as a solvent. Alkaline earth carbonates and titanium oxide were used as precursors for the titanate system, and alkaline earth carbonates and zirconium oxide were used as precursors for the zirconate system. It was found that both systems form solid solutions throughout the composition range. The implications of these results with regards to the applicability of the molten salt method as a tool to investigate low temperature phase equilibria are discussed.

YBa2Cu3O7 (123) samples with varying Y2BaCuO5 (211) concentrations (0 mol%, 20 mol%, 28 mol%, and 50 mol%) were synthesized by the melt-growth process. Microstructural characterizations were done using x-ray diffraction (XRD), optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). It was found that 123 platelet width, crack width between the platelets, and 211 particle size decreased systematically with increasing 211 concentration. TEM study showed that there is a critical radius of curvature (rc ≤ 0.2 μm-0.3 μm) of the 123/211 interface where defects/contrasts of strain field start to appear, and these defects are believed to be responsible for pinning the magnetic flux. Microhardness measurements showed that Vickers hardness (VHN) increases with increasing 211 content. Critical current density (Jc) values obtained from magnetization measurements using a SQUID magnetometer were found to increase in melt-grown samples by the addition of 211 content.

We have compared the microwave-hydrothermal (M-H) processing with conventional hydrothermal (C-H) processing in the preparation of two layered anion exchangers, i.e., Mg3Al(OH)8NO3 · nH2O and Ni1-xZn2x(OH)2(CH3COO)2x · nH2O. Both these phases can be crystallized more rapidly (an order of magnitude) under M-H processing compared to C-H processing. The above layered mixed basic salt of Ni and Zn was found to exhibit very high selectivity for PO4= (Kd = 15,000). Its order of selectivity for various anions in the presence of 0.1 N̲ NaC1 (ratio of C1- to anion in question is 100) increases as follows: PO4= ≫ SO4= > NO3-.

The Zn–22% Al eutectoid alloy is capable of exhibiting very high superplastic elongations, in excess of 2000% in tension, when the grain size is in the range of ∼ 1–10 μm. This paper describes the fabrication of a submicrometer grain size in the Zn–22% Al alloy by subjecting the samples to intense plastic straining in torsion under high pressure (∼5 GPa) at room temperature. Observations after straining revealed a heterogeneous microstructure with grain sizes in the range of ∼0.1–0.5 μm. As a result of the low melting temperature of the alloy, the high internal stresses introduced by torsion straining are relaxed and the grain boundaries are close to an equilibrium configuration.

We report on the properties and characterization of SrBi2Ta2O9 (SBT, or Y − 1) thin film capacitors for ferroelectric random access memory (FERAM) applications. The films were prepared by spin-coating from carboxylate precursors. The remanent polarization (Pr) was 5−6 μC/cm2 and the coercive field was ∼55 kV/cm. Excellent fatigue endurance was observed up to 1011 cycles. Auger analysis indicates bismuth diffusion through the Pt electrode after capacitor anneal which might require excess Bi in the precursor solution for stoichiometry control. No detectable amount of α emission was found from SBT films, which reduces the possibility of soft error when used in the memory devices.

A thermal wave methodology for monitoring the thermal conduction of ceramic coatings with accumulating mechanical damage is described. Tests are conducted on a model alumina coating containing laminar defect intralayers. Controlled subsurface damage introduced with a spherical indenter is observed using a presectioned specimen. Microcrack damage accumulates progressively with increasing contact load and number of cycles. Associated changes in thermal diffusivity, specifically in the through-thickness direction, are imaged and quantified point-by-point using laser-generated thermal waves. The effective thermal resistance of the coating increases with crack density, up to the point of failure.

Methanol decomposition on a clean polycrystalline copper oxide surface was studied by x-ray photoelectron spectroscopy (XPS). Methanol was adsorbed at 133 K and desorbed over a broad temperature range. When CuO was exposed to a very low dose of methanol vapor, dissociative adsorption takes place, leading to the formation of CH3O and H2O. This is attributed to the presence of preadsorbed oxygen on the CuO surface.

The decomposition of almost fully reacted (Bi, Pb)2Sr2Ca2Cu3Ox (BSCCO-2223) tapes caused by heating in 1 atm of pure O2 at 825 °C has been studied. It was found that partially decomposing 2223 tapes to a mixture of Bi2Sr2Ca1Cu2Oy, (Ca, Sr)2PbO4, and other secondary phases reduced the critical current density (77 K, 0 T) from ∼20 kA/cm2 to nearly zero. Reheating the tapes in 7.5% O2 restored the 2223 phase and, while there was some degradation of the 2223 grain alignment due to residual secondary phase growth, the critical current density was also restored to nearly its original value. We hypothesize that such a decomposition/reformation process can be useful in increasing the connectivity and relative density of polycrystalline 2223, by encouraging the formation of a liquid phase which heals residual cracks in the BSCCO core.

Superconductor-normal-superconductor (SNS) edge junctions consisting of YBa2Cu3O7/YBa2Cu2.79Co0.21O7−x/YBa2Cu3O7 were fabricated on (001) YSZ substrates using laser deposition. In contrast to other SNS junctions, e.g., with La0.5Sr0.5CoO3, CaRuO3, or SrRuO3 as the barrier layer, these devices do not display an excess normal-state resistance. High-resolution and conventional transmission electron microscopy (TEM) techniques were employed to investigate the SN interface structure and possible interface defects. Results are compared to recent TEM investigations of CaRuO3 SNS junctions.

Large YBa2Cu3O7−x (Y123) single crystals (larger than 13 mm cubed) have been grown along the c-axis reproducibly by the modified pulling method. The crystallinity of Y123 single crystal was investigated by x-ray diffraction and x-ray topography. Crystals grown from an MgO single crystal seed had some low angle subgrain boundaries which tilted 0.1–0.8° from each other. These grain boundaries originated from the seed crystal, and the subgrains were extended along the growth direction from the seed crystal. Y123 single crystals with no marked subgrains in the whole area were obtained by using Y123 single subgrain crystal seeds. FWHM of the x-ray rocking curve for the crystal so produced was about 0.14°, which was much better than the spectrum consisting of several separated peaks obtained from the previous crystals. Tc onset of the annealed sample was about 93.6 K, and the transition width was about 0.9 K. The low angle subgrain boundaries did not seem to be effective pinning centers for the magnetic flux.

A new designed reaction chamber with new relative distribution of filament and substrates has been adopted in order to increase the deposition area of diamond films and thus increase the deposition efficiency in conventional hot filament chemical vapor deposition (HFCVD) systems. The relatively small reaction chamber was cuboid shaped (50 × 25 × 25 mm3) and composed of molybdenum wafers. It was established in the vacuum chamber. A tungsten filament was hung up vertically in the center of the small chamber and parallel to the gas flow path. At the four inner sides of the reaction chamber, four Si(100) substrates (30 × 10 × 0.5 mm3) were installed to grow diamond films. The deposition results indicate that uniform diamond films can be obtained on the four substrates, and the film growth rate is the same at both ends of the substrates. The diamond film growth rate was about 1−2 μm/h, which is similar to those of the conventional HFCVD method. Thus, the deposition area and efficiency can be increased four times in the case without the filament number, gas flow rate, and power consumption.

A new method is proposed to prepare bulk nanocrystalline alloys by quenching alloy melts under high pressure. Due to application of pressure to solidification processes, the nucleation rate is increased whereas the growth rate of nuclei decreased with increase of pressure, which makes it possible to obtain bulk ingots with nanometer-sized crystalline grains if appropriate pressure, temperature, and cooling rate are selected. The as-pressure-quenched products are cylinder-like with diameter about 4 mm and height several millimeters. This method can produce dense, free-porosity bulk nanocrystalline alloys with clean crystalline interfaces, promising use for experimental research and technological applications.

The inherently weak mechanical properties associated with monolithic high-temperature superconductors (HTS) can be improved by introducing properly selected strong ceramic whiskers into the HTS materials. In this research, processing and superconducting properties of monolithic Pb-doped Bi-2223 (BPSCCO) and MgO whisker-reinforced BPSCCO HTS composite materials have been systematically studied. A solid-state processing method is successfully developed to fabricate the (MgO)w/BPSCCO composite. The HTS composite contains a dense and highly pure BPSCCO matrix phase with a preferred grain orientation, which is reinforced by MgO whiskers randomly oriented in the plane perpendicular to the hot-pressing direction. The HTS composite material is shown to exhibit excellent superconducting properties. For example, a transport Jc measured at 77 K in a zero field has been obtained to exceed 5000 A/cm2 in a (MgO)w/BPSCCO composite with 10% MgO whiskers by volume. Relationships among solid-state processing variables, HTS phase development, and superconducting properties of the monolithic BPSCCO and the HTS composite are established in the paper.

Iron nitride and iron carbonitride (ICN) ultrafine particles (20–80 nm in size) have been synthesized by laser-induced pyrolysis of the Fe(CO)5–NH3–C2H4 system. The oxidation behavior, surface morphologies, and structural characteristics as well as magnetic properties of these particles are reported and discussed. It is found that the presence of very thin carbon coating (1–2 nm) on the ICN particles plays an important role in preventing the oxidation of the particles. Accordingly, the ICN ultrafine particles exhibit higher saturation magnetization (142 emu/g) than the iron nitride ones (124 emu/g).

Borosilicate glass films were made by the sol-gel method from tetraethoxysilane and trimethylborate precursors. The precursor or glass composition at each stage of processing was analyzed to determine the sources of boron loss. The films were heated in a furnace and with a laser to compare boron volatilization by the two heating methods. The films were characterized by infrared spectroscopy, ellipsometry, induction-charged plasma spectroscopy, and Auger microscopy. The highest losses of boron occurred during coating and low temperature (<500 °C) furnace firing. Films with the highest boron concentrations were made by dip coating and rapid firing, either with a laser or by placing them into a hot furnace. Infrared spectroscopy revealed Si–O–B bonds, indicating incorporation of boron into the borosilicate glass structure for laser- and furnace-fired films.

The HOMO-LUMO gaps have been estimated in a graphite-like sp2 carbon network with a progressive increase in the fraction of sp3 carbons, taking into account several possible structural alternatives for each composition. The gap is shown to increase exponentially with the fraction of sp3 carbons. Accordingly, the gap in a diamond-like sp3 network decreases with the increase in the fraction of sp2 carbons.

Ball milling is a technique used extensively in metallic powders to obtain adequated properties for their applications. In this study we show that this technique is also useful for preparing organic molecular alloys. Pentaglycerin/Pentaerythritol alloys have been obtained mechanically at room temperature. Calorimetric and crystallographic characterizations establish that the mechanically obtained alloys have the same solid crystalline structure and transform to the plastic phase as the conventionally prepared alloys from the melt of the pure compounds.