Thin films of the 80 K-phase of BiCaSrCu-oxide superconductor having the composition of Bi2Ca1.05Sr2.1Cu2.19Ox and high degree of crystalline perfection have been grown on c-axis oriented twin free single crystal substrates of NdGaO3. This has been achieved by carefully establishing the growth conditions of the liquid phase epitaxy (LPE) experiments. The temperature regime of 850 °C to 830 °C and quenching of the specimens on the termination of the growth period are found to be pertinent for the growth of quasi-single crystalline superconducting BCSCO films on NdGaO3 substrates. The TEM analysis reveals a single crystalline nature of these films which exhibit 100% reflectivity in infrared regions at liquid nitrogen temperature.

Tracer self-diffusion of Ba and Y and the diffusion of Dy, Ho, and Gd, which substitute for Y, have been measured in polycrystalline YBa2Cu3Ox over temperature and oxygen partial pressure ranges of 850 to 980 °C and 103 to 105 Pa, respectively. The diffusion of Ba is slower than that of oxygen or copper, with a high activation energy of about 890 ± 80 kJ/mole. Large anisotropy has also been observed, with diffusion along the c-axis being more than three orders of magnitude slower than diffusion in randomly oriented polycrystals. Diffusion coefficients of Ba were, within experimental uncertainty, independent of oxygen partial pressure over the range measured. The diffusion coefficients of the Y-site species were nearly identical and an activation energy of about 1.0 MJ/mole was estimated, in agreement with that for high-temperature deformation. Attempts to speed up the kinetics through creation of point defects on the Y site by doping proved to be unsuccessful. These results are compared to cation diffusion in cubic perovskites and simple oxides.

In the preparation of YBa2Cu3Oy (Y-123) superconductor, the coprecipitation method was frequently used in various solution systems due to advantages such as good homogeneity, low reaction temperature, fine and uniform particle size, easy scale-up, and economical concerns. In this paper, a detailed study of different competitive reactions such as dissociation, precipitation, complex formation, and association involving metal ions, oxalate ion, and diethylamine species is performed. The study aids in understanding the precipitation and yields an optimal coprecipitation condition for the title system. A series of experiments are also conducted which confirm that the as-derived optimal condition may be extensively applied to other systems.

An evaluation of the effects of oxygen partial pressure (pO2) on sintering behavior and the resulting microstructure of YBa2Cu3Ox (YBCO) indicates that sintering kinetics are enhanced at reduced pO2. The density of specimens sintered at 910 °C increased from 79 to 94% theoretical when pO2 was decreased from 0.1 to 0.0001 MPa. It is believed that increase in density with decrease in pO2 is the result of enhanced sintering kinetics, due probably to increased defect concentration, decreased activation energy of the rate-controlling species, and possibly the presence of a small amount of liquid phase. Sintering at 910 °C resulted in a fine-grain microstructure, with an average grain size of ≍4 μm. Such a microstructure results in reduced microcracking. Consequently, strength as high as 191 MPa is achieved. Reduced microcracking may have important implications for developing microstructures with improved critical current density.

The crystal structures of YBa2Cu3O7−x thin films deposited on MgO(100) substrates have been investigated by cross-sectional transmission electron microscopy (TEM). At a substrate temperature of 670 °C, Cu–O chains become wavy. Stacking faults are formed between the Cu–O chains. Therefore, the domains with c-axis lattice constants of 15 Å, 27 Å, and 39 Å are observed. By applying a biasing voltage of + 300 V, deviation in the c-axis orientation is reduced compared to that at an unbiased condition; even some grain boundaries remain. Near substrate surfaces, deviation of the c-axis direction from the substrate normal increases with a decreasing substrate temperature from 700 °C to 670 °C. Application of a substrate bias voltage of +300 V improved the heteroepitaxial growth of the c-axis oriented YBa2Cu3O7−x.

Superconducting YBa2Cu3O7−y (YBCO) films having a thickness of 1 μm were prepared on SrTiO3(100) and MgO(100) by the dipping-pyrolysis process using a low-p(O2) annealing method. Heat-treatment conditions were varied along the upper limit of the stability region of the YBCO phase. Films on SrTiO3(100) exhibited strong c-axis orientation with sharp rocking curves (FWHM = 0.8°). The highest Tc,zero of 87 K was obtained for the film heat-treated at 750 °C. On the other hand, films on MgO(100) showed broader rocking curves and their Tc's remained lower. Moreover, Ag addition was found to enhance the Tc values (Tc,zero = 91 K) of films on SrTiO3 heat-treated at 750 °C.

The film crystallinity and nature of the interface between Y1Ba2Cu3O7−x (YBCO) films and (100)-oriented MgO substrates are revealed using results from x-ray line broadening analysis, x-ray pole figure analysis, and simple models for interface types. The superconductor film was grown using Activated Reactive Evaporation (ARE) at 675 °C. The results show that the interface can be treated as semicoherent with interfacial dislocations whose spacing depends on the in-plane orientation relationship between YBCO and MgO. For the orientation relationship (100) YBCO parallel to (100) MgO, the spacings between dislocations are 9 lattice spacings of MgO in the a direction and 11 lattice spacings of MgO in the b direction. For the orientation relationship (110) YBCO parallel to (100) MgO, the spacing between dislocations is 2 lattice spacings of MgO (or 4 plane spacings of (200) MgO—see Ref. 10). The x-ray based method used here can be an addition to or a replacement for the cumbersome cross-sectional TEM technique (for the YBCO system) to view the interface.

The CeO2-added Y–Ba–Cu–O oxides were prepared by two different processes, the conventional solid-state reaction process and the partial melt process using powders, to examine the effect of the dopant on microstructure, microhardness, and superconductivity. In the solid-state reacted sample, most of the added CeO2 was converted to a form of BaCeO3, but some might enter into the 1-2-3 phase, resulting in the orthorhombic-to-tetragonal phase transition that accompanied the disappearance of twin structure in 1-2-3 grains. In the partially melted sample, however, the phase change was not observed up to 5 wt. % of CeO2. All the added CeO2 in these samples was consumed to form only BaCeO3 which was finely dispersed in large 1-2-3 grains during the peritectic reaction stage. The zero resistance temperature (Tc) of the solid-state reacted sample gradually decreased with increasing CeO2 content due to the phase change and the formation of BaCeO3, whereas the Tc of the partially melted sample was nearly constant regardless of CeO2 content up to 5 wt. %, owing to the separation of the second phase from the 1-2-3 superconducting phase. Microhardness of the partially melted sample increased with increasing CeO2 content. The strengthening effect appears to come from the composite system where the fine BaCeO3 particles are dispersed in a 1-2-3 matrix.

Superconducting YBa2Cu4O8 ceramics were synthesized by the sol-gel method using corresponding metal acetates as starting materials, water as solvent, and tartaric acid under 1 atm oxygen pressure. YBa2Cu4O8 powder was obtained as a single phase by heating the gel at 780 °C for 30 h in flowing oxygen. Tc was 80 K from magnetic susceptibility measurements. Pelletizing and sintering this powder revealed Tc (onset) of 87 K and Tc (end) of 78 K from resistance measurements. YBa2Cu4O8 pellets sintered at 780 °C for 30 h in O2 also consist of a single phase with Tc (onset) of 85 K and Tc (end) of 75 K.

Dense polycrystalline Bi2Sr1.7CaCu2Ox (2212) was deformed from 780–835 °C in oxygen partial pressures, Po2, of 103 to 2 × 104 Pa. Results could be divided into two stress regimes: one at lower stress in which the steady-state creep rate, ∊, was proportional to stress, γ, having an activation energy of 990 ± 190 kJ/mole and being independent of PO2, and another at higher stress in which ∊ was proportional to σn, with n ≍ 5–6. Transmission electron microscopy supported the interpretation that in the lower-stress viscous regime, creep was controlled by diffusion, whereas dislocation glide and microcracking were responsible for strain accommodation at higher stresses.

Bismuth-based high Tc superconductors have been prepared as fibers by a technique of melt extraction. As-made, the fibers are amorphous with diameters ranging from 0.7 μm to 100 μm and lengths of up to 5 cm. The fibers were subsequently transformed into high Tc superconductors by heat treatment in air. Superconducting transitions at 105 K and 82 K were measured in annealed fibers of initial composition Bi1.8Pb0.2Sr2Ca3Cu4Ox by SQUID magnetometry. The volume fractions of superconducting phases were estimated to have lower bounds of 30% for 2212 and 5% for 2223. The crystallization process has been studied by differential scanning calorimetry, electron microscopy, and x-ray diffraction. Crystallization involves first the formation of the Bi-2201 phase and a bcc phase with lattice parameter a = 0.425 nm before finally significant fractions of both the Bi-2212 and Bi-2223 phases are formed.

Nuclear microscopy combines a range of MeV light ion beam analytical techniques such as Proton Induced X-ray Emission (PIXE), Rutherford Backscattering Spectrometry (RBS), and Scanning Transmission Ion Microscopy (STIM). One of the main advantages of using MeV light ion beams for materials characterization is the large analytical volume due to their high penetration depth. This paper shows how nuclear microscopy is used to determine the size and distribution of Pb precipitates in a 40 μm thick alloy sample with a nominal composition of Al–5 wt.% Pb.

In this paper, we have demonstrated that very perfect thin multilayers of the Cu/Ni system can be prepared with coherent interfaces if the layer modulation wavelength is in the 10 nm range. At modulation thicknesses above about 60 nm, the interfaces become incoherent. We have injected a crack into a coherent interface in the 10 nm case which has generated dislocations into the interface forming the crack plane, as well as into the layers adjacent to the crack plane. The dislocations injected into the crack plane presumably form misfit dislocations on that interface, and are grouped so close to the crack tip that individual dislocations are not completely imaged. The dislocations injected into the adjacent layers are distributed rather widely. We have analyzed the dislocation emission from a crack in the fcc geometry appropriate to the multilayers using a simplified elastic theory developed for cracks in homogeneous materials. The mixed mode loading which the misfit stresses are expected to produce lead one to expect these materials to be ductile and to have high toughness. Very high dislocation densities on the crack plane near the crack, however, may lead to a brittle mode of failure, which is beyond the purview of the elastic theory. The dislocations are observed to have strong interactions with alternating interfaces in the multilayers, and this effect could be due to elastic bunching of the dislocations at alternating interfaces caused by the misfit stress.

The effect of additional elements (Si and Co) on the behavior of copper polycrystalline alloy under static and dynamic compression was studied. Relations between the deformation microstructure and the mechanical behavior have been investigated. In the Cu–Si alloys, the SFE depends on additional element content and the SFE level controls the dissociation of perfect dislocations into partial ones. In the Cu–Co alloy, Co induces precipitation and the dislocation repartition is uniform if the precipitates are coherent. When the precipitates become semicoherent, there is formation of dislocation walls around the precipitates.

Three-dimensional chemical maps by Secondary Ion Mass Spectrometry (3D-SIMS), XPS spectroscopy, and SEM-EDAX microscopy were employed in order to investigate the effects of accelerated fatigue tests on crack formation in 95.5% Pb–2% Sn–2.5% Ag and 95% Pb–5% Sn solder joints. These alloys are used in the die bonding of electronic power device assemblies. The results show that cracks form by Sn-depletion from the inner regions of the soldered joint. Simultaneously, there is a recrystallization of the Pb-rich phase in the same regions of the joint. The crack occurs at a critical number of cycles when a Sn-depleted region is formed, yielding weaker inner layers with lower shear strength. A possible explanation of the Sn-depletion is also discussed.

Using the all-electron full potential linearized augmented plane wave (FLAPW) total energy method, the influence of P impurity atoms on the cohesion of the Fe Σ3[1$\overline 1$10](111) grain boundary is studied through direct comparison of phosphorus/iron interactions in the grain boundary and free surface environments. The calculated nearest P–Fe distance in P/Fe(111) is 2.14 Å—amounting to a 5% contraction compared to that (2.26 Å) measured for the Fe3P compound and assumed for the P–Fe grain boundary. The polar-covalent P–Fe chemical bonding, which is a strong function of the P–Fe interatomic distance, is thus stronger on the Fe(111) surface, while P reduces the spin polarization of the surrounding Fe atoms more efficiently in the grain boundary environment. These effects are examined in terms of the relative segregation energies affecting the work of boundary fracture.

The structural transition between the metastable fcc and hcp crystalline solid solutions in the Ni–Ru system has been studied as a function of composition using the mechanical alloying technique. At the transition point, the spacings between the close-packed planes of the metastable fcc and hcp phases are the same. No amorphization is observed at the interfaces. This mechanically induced phase transition has been studied by x-ray diffraction, transmission electron microscopy, and differential thermal analysis.

Finely dispersed metal powders have been obtained after chemical reduction of Ni and Co acetylacetonate by lithium aluminum hydride in tetrahydrofuran at low temperature. The Al/Ni and Al/Co stoichiometry of the as-reduced powders was 1.1 and 1.2, respectively. The structure and thermal stability of the as-reduced powders were affected by the temperature of reduction. For the NiAl powders it was found that the thermal treatment initially induces a separation of highly unstable Ni(Al) and Al(Ni) solid solutions, which subsequently react to give a single NiAl phase of cubic structure not reported in the equilibrium phase diagram. Conversely, the reduction of cobalt acetylacetonate directly gives a cubic metastable phase, from which precipitates some hexagonal form of Co after treatment at 450 °C.

The room-temperature and 700 °C tie lines of the early transition metal–Si–Cu ternary systems have been calculated for the metals Cr, Mo, Nb, Ta, V, and W. The tie lines are determined by considering only binary and elemental phases in observance of strict stoichiometry and zero solid solubility. We find that copper is stable with the majority of transition metal silicides under consideration at 700 °C. The result is relevant to the design of stable copper metallizations for silicon.

The nucleation and growth of diamond crystals on single crystal copper surfaces has been studied. Microwave plasma enhanced chemical vapor deposition (MPECVD) was used for diamond nucleation and growth. Prior to diamond nucleation, the single crystal copper surface is modified by carbon ion implantation at an elevated temperature (∊820 °C). This procedure leads to the formation of a graphite film on the copper surface, resulting in an enhancement of diamond crystallite nucleation. A simple lattice model has been constructed to describe the mechanism of diamond nucleation on graphite as 〈111〉diamond parallel to 〈0001〉graphite and 〈110〉diamond parallel to 〈11$\overline 1$0〉graphite. This leads to a good understanding of diamond growth on carbon-implanted copper surfaces.