Due to the highly anisotropic properties of BSCCO superconductors, the bulk properties of these materials can be greatly affected by preferential orientation. Substantial c-axis orientation normal to the desired direction of current flow has been demonstrated by centrifugally slip casting lead-doped BSCCO-2223. The strong preferred orientation developed in the centrifugally slip-cast material demonstrates high critical current potential.

Stabilization of zirconia into cubic phase is achieved by partly substituting Zr4+ with Mn4+ ions (5–30 mole %) via hydroxide gel formation and subsequent calcination at 773 K and is supported by XRD and IR data. A linear correlation between the lattice parameter and the Mn content confirms the incorporation of Mn into ZrO2. The XPS and TPR results provide some evidence for the presence of Mn4+ ions in these samples which have a surface area of about 100 m2 g-1 and are stable in the cubic phase up to 973 K. On reduction above 973 K, the cubic phase is stabilized probably by Mn2+ ions.

Reactive liquid phase sintering of the YBCO films prepared from carboxylate solution precursors was investigated. A liquid phase was formed by the BaO—CuO binary compound at 620 °C, which facilitated the crystallization and growth of the YBCO grains. Strong capillary forces associated with the liquid phase sintering resulted in a dense, highly oriented microstructure. The YBCO films processed by this reactive liquid phase process showed Tc(zero) = 90.2 K and Jc = 1.3 × 105 A/cm2 at 77 K. The (006) rocking curve measurement indicated excellent grain orientation with a FWHM better than 0.2°. A secondary ion mass spectroscopy (SIMS) study showed uniform film composition, and the film/substrate interaction zone was limited to ≈0.1 μm. Average film roughness was about 32 nm.

Texture formation of the partially melted process of solution-spun Y1Ba2Cu3Ox, was examined to enhance the reproducibility of the high Jc of the filament. The effect of Rh addition on the texture formation was also investigated. Controlling the cooling rate through peritectic temperature to produce 123 is the key for obtaining the reproducible high Jc. A well-aligned texture in the present filament needs a relatively high cooling rate for the following 123 crystal growth, such as 40 °C/h. Addition of Rh promotes the preparation of the 123 phase and enhances the Jc.

The effects of annealing temperature and oxygen partial pressure [p(O2)] were investigated on the crystallization and orientation of superconducting YBa2Cu3O7-y (YBCO) films on SrTiO3(100) prepared by the dipping-pyrolysis process. Annealing conditions for precursor films consisting of a Y2O3—BaCO3—CuO mixture were varied in the temperature range 700–850 °C and initial p(O2) range 2 × 10-4-10-2 atm followed by pure O2 treatment. Three different types of crystallization behavior were observed. The c-axis-oriented epitaxial YBCO films were obtained on the lower p(O2) and higher temperature side in the p(O2)-T diagram. The c/a-axis-oriented growth was observed in films heat-treated at 750–800 °C under p(O2) of 10-3 atm. In addition, mixtures of YBCO and YBa2Cu4O8 resulted when the films were annealed at 700 °C.

Syntheses of Al-based metastable alloys from powder mixtures of elemental Al and amorphous Fe78Si12B10 [x at. % Al + (100 — x) at. % (Fe78Si12B10)] alloy by mechanical milling (MM) using a planetary ball mill are investigated. X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are used to characterize their structure during the MM process. For the powder mixture with low content of Al (x = 75, 82), fully amorphous material can be obtained by MM, while for the milled product with a high content of Al (x = 90), nanocrystalline Al and amorphous phases are obtained. During the initial milling stage, the Al atoms are dissolved into the amorphous Fe78Si12B10 matrix by heavy deformation. Consequently, the Al-enriched homogeneous amorphous alloys are produced with the disappearance or shrinkage of diffraction peaks of Al in the XRD pattern. Further milling of the powder mixture with 75 at. % Al results in the crystallization of amorphous phase and the formation of nanocrystalline Al3Fe type phase. The crystallization products of all as-milled samples are very similar, composed of Al13Fe4 and AlFe3 phases. It is suggested that the kinetics of nucleation and growth favor the formation of amorphous phase due to the existence of amorphous phase initially. The amorphization reaction by mechanical milling is diffusion process, but defects and strain also play an important role.

Atomistic computer simulation with embedded atom method potentials has been performed to study the energetics and structures of point defects in L12Ni3A1 and B2 NiAl. The large size of Al atoms plays a dominant role in the relaxed atomic configurations of vacancies and antisite defects in the system. In both Ni3Al and NiAl, it was found that excess Ni can be accommodated by Ni in Al sites. Accommodation of excess Al by locating Al in Ni sites is not energetically favorable in NiAl. The most stable di-vacancy configuration is two vacancies as first nearest neighbors in Ni sublattices for Ni3Al and as second nearest neighbors in Al sublattices for NiAl. General attraction of two vacancies in Ni3Al was found. On the contrary, vacancies in NiAl show repulsive interaction in several cases. This accounts for the existence of structural vacancies in B2 NiAl. The effects of different degrees of random disorder on the lattice parameters were evaluated, and it was found that these effects can be correlated with the local distortion around antisite defects using a simple model.

We have studied the oxidation of thin epitaxial Fe(100) films on MgO(100) with and without an Au(100) protecting cap by x-ray reflectivity measurements. The oxidation was carried out under atmospheric conditions between 20 δC and 200 δC. The results are compared to the oxidation of Fe(110) oriented films on Al2O3(1120) substrates with an Au(111) cap. Auger electron spectroscopy before and after oxidation was carried out for sublimentary chemical information of the surface. For the uncovered Fe films we observe smoothly growing oxide films at the surface during oxidation at elevated temperatures. As expected, the Au(100) cap serves as an effective shield against oxidation, while the Au(111) cap, surprisingly, does not. In the case of Au/Fe/Al203, we find Fe2O3 formation at the surface of the Au layer at 200 δC. The different behavior of Au(100) and Au(111) is discussed in terms of stacking faults and/or domain structure occurring in the latter case during epitaxial growth.

Superstructuring in the new compound Fe1.89Mo4.11O7 has been elucidated by transmission electron microscopy. This compound is a member of the family M2MO4O7 and has both iron and molybdenum atoms occupying octahedrally coordinated sites in the structure, represented by Fet(Fe0.89M0.11)0Mo4O7. The superstructuring, detected only by electron diffraction, involved tripling of all three lattice parameters of the subcell. The subcell was structured by single crystal x-ray diffraction [Imma, no. 74, a = 5.9793(5) Å, b = 5.7704(4) Å, and c = 17.036(1) Å]. This structure type contains a close-packed arrangement of Mo4O7 units, which are infinite chains of trans edge-shared molybdenum octahedra running parallel to b*. Two different coordination environments are observed for the cations. Parallel to the a* direction, infinite edge-sharing MO6 (M = 89% Fe or 11% Mo) octahedra are observed. The second cation site, with nearly tetrahedral coordination by oxygen, is filled solely by iron. The superstructure can be rationalized by a regular arrangement of iron and molybdenum atoms in the octahedrally coordinated cation sites.

Epitaxial LaNiO3 thin films have been grown on SrTiO3 and several other substrates by pulsed laser deposition. The films are observed to be metallic down to 15 K, and the temperature dependence of resistivity is similar to that of bulk LaNiO3. Epitaxial, c-axis oriented YBa2Cu3O7-x films with good superconducting properties have been grown on the LaNiO3 (100) films. I-V characteristics of the YBa2Cu3O7-x-LaNiO3 junction are linear, indicating ohmic contact between them.

The impression creep behavior of lead was investigated using a 100 μm diameter punch at ambient and elevated temperatures (433 K-563 K) under punching stresses of 6–70 MPa. The results were compared with the data obtained from conventional creep tests reported in the literature. Unlike the indentation creep test, the impression creep test showed a steady-state velocity after a short transient period when the flat-end cylindrical punch was pushed against the lead surface by a constant load. Both the temperature and stress dependences were comparable to those of the constant stress tensile creep tests under similar conditions. A master curve for lead was established by collecting data from the impression creep tests and the constant stress tensile creep tests. The indentation creep measurements for lead were included also. However, the indentation data depend on the load applied.

A new ternary material Co3(SbTe3)2 was prepared by using a rapid precipitation metathesis reaction between the Zintl material K3SbTe3 and CoCl2 in aqueous solution. The dc specific resistivity of this material is in the region for metallic conductors (p = 2.75 × 10-3 Ω-cm). The dc magnetic susceptibility of Co3(SbTe3)2 is reported over a 2.2 K-300 K temperature region, and the material is characterized as a spin glass with a freezing temperature of about 5 K. Magnetization data are also reported as both thermal remanent magnetization and isothermal remanent magnetization as a function of magnetizing field and temperature. When cooled well below the glass freezing temperature, the frozen spin glass has been observed to exhibit photomagnetic effects consistent with a disruption of the spin-glass state caused by uv-radiation.

The absolute concentration of methyl radicals (CH3) and the mole fraction of acetylene (C2H2) are measured in a hot filament chemical vapor deposition (CVD) system both during and after an initial pretreatment that has been used successfully in microwave plasma and oxyacetylene torch CVD systems to produce more uniform and higher density crystal nucleation. The pretreatment technique, which consists of deposition for a relatively short time with a high input concentration of hydrocarbon in the feed gas, was studied for both methane (CH4) and C2H2 as the input hydrocarbon diluted in H2. Scanning electron micrographs of diamond films deposited under the conditions studied indicate that the pretreatment using CH4 is not effective in increasing the crystal nucleation density, but is moderately effective in increasing the crystal size. The C2H2 pretreatment has no apparent effect upon either the crystal size or nucleation density. The spectroscopie measurements suggest that the surface condition of the filament is the prominent factor affecting the gas phase chemistry both during and after the pretreatment stage.

Copper and diamond both have cubic crystal structures and similar lattice constants, making Cu an excellent candidate substrate for the heteroepitaxial growth of electronic device quality diamond. In this study a Cu substrate preparation method was developed to obtain large-area, free-standing polycrystalline diamond films. Concurrently, a statistically designed experiment was used to maximize the diamond film quality and resulted in (111) and (100) faceted films of quality comparable to or better than those grown on Si. The diamond films were analyzed by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy.

The first direct electrical resistance measurements performed on a single carbon nanotube bundle from room temperature down to 0.3 K and in magnetic fields up to 14 T are reported. From the temperature dependence of the resistance above 2 K, it is shown that some nanotubes exhibit a semimetallic behavior akin to rolled graphene sheets with a similar band structure, except that the band overlap, Δ ≈ 3.7 meV, is about 10 times smaller than for crystalline graphite. In contrast to graphite which shows a constant low-temperature resistivity, the nanotubes exhibit a striking increase of the resistance followed by a broad maximum at very low temperatures. A magnetic field applied perpendicular to the sample axis decreases the resistance. Above 1 K, this behavior is consistent with the formation of Landau levels. At lower temperatures, the resistance shows an unexpected drop at a critical temperature which increases linearly with magnetic field. These striking features could be related to the unique quasi-one-dimensional structure of the carbon nanotubes.

The reaction of tetraethoxysilane (TEOS) and the subsequent deposition of SiOx on the basal plane and edges of highly oriented pyrolytic graphite (HOPG) were studied. Interfacial bonding and surface morphologies resulting from different reaction conditions were probed using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), temperature programmed desorption (TPD), and high resolution electron energy loss spectroscopy (HREELS). The initial reaction of TEOS was found to occur at surface defects. STM images indicated that SiCx films do not grow layer-by-layer, confirming earlier indirect observations to that effect.

Epitaxial β-SiC (3C) films were grown on (0001) 6H-SiC and 15R-SiC substrates by chemical vapor deposition (CVD). TEM characterization revealed that films on both substrates exhibited large areas of atomically flat, coherent interfaces. However, when 3C-SiC films were grown on 6H substrates, double position boundaries (DPB's) were frequently observed, and islands of 6H were occasionally embedded in the predominantly 3C film. In contrast, films of 3C-SiC grown on 15R substrates exhibited relatively few DPB's and only occasional islands of 15R. A model of interlay er interactions in SiC was applied to predict the atomic structures at both 3C/6H and 3C/s15R interfaces, and these predictions were consistent with experimental observations of the interfaces by TEM. The observed interface structures and defect distributions were attributed to a microscopic kinetic mechanism of terrace growth. Consideration of step energies and growth kinetics led to the prediction that DPB's can be avoided by growing 3C-SiC films on 15R-SiC substrates.

Undoped and lanthanide (La and Nd) doped Pb(ZrxTi1-x)03, i.e., PZT, ferroelectric thin films were prepared by metallorganic decomposition (MOD) and spin-coating. The precursors for making the undoped PZT films were derived from lead acetate, zirconium n-propoxide, and titanium isopropoxide. In addition, lanthanum acetylacetonate and neodymium acetate were introduced into the precursor solution to accomplish the doping of the corresponding elements. Both undoped and doped PZT films were coated onto Pt/Ti/Si02/Si and single-crystal sapphire substrates to various thicknesses and annealed at a range of temperatures and times. The effects of lanthanide dopants in PZT films were studied with regard to microstructure, Curie temperatures, crystal distortion, optical properties, and electrical properties. The results indicate that the addition of La and Nd dopants tends to enhance perovskite phase formation and improve the packing densities and electrical properties of PZT films.

Single phase BaTi03 thin films were prepared by metal-organic deposition (MOD) using barium 2-ethylhexanoate and titanium dimethoxy dineodecanoate as the metal-organic precursors. A series of experiments was conducted on the metal-organic spin-coated films and their correspondingly annealed samples by employing experimental techniques ranging from thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and scanning electron microscopy (SEM), to various optical property characterization methods. A better understanding has been achieved regarding the metal-organic decomposition mechanism, the solid-state BaTi03 film formation and crystallization process, as well as the relationship between the structure and the optical properties of the prepared films. The conclusions of our experiments are as follows: Upon annealing the barium 2-ethylhexanoate spin-coated films, barium carbonate (BaC03) is formed at a relatively low temperature of 300 °C, and at an annealing temperature around 700 °C forms the barium peroxymonocarbonate (BaCO4). Upon annealing the titanium dimethoxy dineodecanoate spin-coated films, anatase is first formed at a low annealing temperature about 400 °C and transforms to rutile phase around an annealing temperature of 800 °C. Upon annealing the spin-coated films from the equimolar mixture of barium 2-ethylhexanoate and titanium dimethoxy dineodecanoate formulations, BaTi03 is formed around an annealing temperature of 600 °C via solid-state reaction between BaCO3 and TiO2 (anatase). The structure of MOD prepared BaTiO3 films has several specific features: instead of the columnar structure in physical vapor deposited (PVD) films, the crystal grains in granular shape are characteristic of MOD films, and the crystallites are much larger near the surface of the film than near the substrates. Optical properties of the prepared BaTi03 films have been reported. Optical characterization shows that the scattering losses contribute dominantly to the total optical losses. The relationship between the structure and the optical properties of the prepared films has also been discussed.

Thin films of LiNbO3 were fabricated on sapphire(012), MgO(OOl), and Si(111) substrates by the sol-gel process. Under optimized conditions, films deposited onto sapphire(012) were epitaxially grown. Preferred orientations, however, were not observed in the films on MgO(001) and Si(111) by x-ray diffraction measurements. Morphology of the epitaxial films on sapphire(012) was examined by scanning electron microscopy, which indicated that the films were smooth and had a pore-free surface. Electrical and optical measurements on the epitaxial films revealed that the properties of the films were very similar to those of the single crystalline LiNbO3, while films deposited onto Si(111) did not show any orientational behaviors. The highest quality films with epitaxy were obtained only on sapphire(012). The remaining substrates appeared to be not suitable for growing epitaxial LiNbO3 films by the sol-gel method.