Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

We analyzed the crystallographic c-axis tilt of (001) Y2O3 films grown on biaxially textured Ni–5%W tapes under different oxygen flux conditions. Results show that different tilting mechanisms were effective in films with different oxygen stoichiometry. Moreover, the structure of the film/substrate interface investigated by transmission electron microscopy, and the residual strain of the film investigated by x-ray diffraction were also dependent on the film oxygen content. Although the oxygen stoichiometric Y2O3 sample exhibited a coherent film/substrate interface and the sharpest out-of-plane texture, the films grown under reduced oxygen pressure exhibited a smaller overall c-axis tilt due to formation of interface dislocations and regions in which the film oxygen vacancies ordered to form a lattice superstructure.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

We report a detailed study of the grain orientations and grain boundary (GB) networks in YBa2Cu3O7-δ (YBCO) films ∼0.8 μm thick grown by both the in situ pulsed laser deposition (PLD) process and the ex situ metalorganic deposition (MOD) process on rolling-assisted biaxially textured substrates (RABiTS). The PLD and MOD growth processes result in columnar and laminar YBCO grain structures, respectively. In the MOD-processed sample [full-width critical current density Jc(0 T, 77 K) = 3.4 MA/cm2], electron back-scatter diffraction (EBSD) revealed an improvement in both the in-plane and out-of-plane alignment of the YBCO relative to the template that resulted in a significant reduction of the total grain boundary misorientation angles. A YBCO grain structure observed above individual template grains was strongly correlated to larger out-of-plane tilts of the template grains. YBCO GBs meandered extensively about their corresponding template GBs and through the thickness of the film. In contrast, the PLD-processed film [full width Jc(0 T, 77 K) = 0.9 MA/cm2] exhibited nearly perfect epitaxy, replicating the template grain orientations. No GB meandering was observed in the PLD-processed film with EBSD. Direct transport measurement of the intra-grain Jc(0 T, 77 K) values of PLD and MOD-processed films on RABiTS revealed values up to 4.5 and 5.1 MA/cm2, respectively. As the intra-grain Jc values were similar, the significantly higher full-width Jc for the MOD-processed sample is believed to be due to the improved grain alignment and extensive GB meandering.

Epitaxial lanthanum zirconate (LZO) buffer layers have been grown by sol-gel processing on Ni–W substrates. We report on the application of these oxide films as seed and barrier layers in coated conductor fabrication as potentially simpler, lower cost coated-conductor architecture. The LZO films, about 80–100-nm thick, were found to have dense, crack-free surfaces with high surface crystallinity. Using 0.2-μm YBCO deposited by pulsed laser deposition, a critical current density of 2 MA/cm2 has been demonstrated on the LZO films (YBCO/LZO/Ni–W). Using 0.8-μm YBCO deposited using metal organic decomposition, a critical current density of 1.7 MA/cm2 and a critical current of 135 A/cm have been demonstrated on the LZO barrier layer with a sputtered CeO2 cap layer (YBCO/CeO2/LZO/Ni–W). These results offer promise to replace several of the vacuum-deposited layers in the typical coated conductor architecture (YBCO/CeO2/YSZ/Y2O3/Ni/Ni-W).

In this paper a novel buffer layer architecture consisting of LaMnO3/MgO/TiN is proposed as a suitable structural and chemical template for the epitaxial growth of high-transition temperature (Tc) superconductors on Cu metal surfaces. Using techniques such as high-energy electron diffraction and scanning transmission electron microscopy, we present in situ and ex situ analyses of the buffer-layer and superconductor growth with focus on structural properties of the interfaces formed. While MgO is a good barrier to oxygen diffusion, we find that MgO alone is not a suitable buffer layer due to rapid Cu diffusion. Further, growth of MgO with a single epitaxy can be hindered by the presence of impurities such as S, which form strongly bonded superstructures on the metal surface. With the addition of a TiN layer as a barrier to Cu diffusion, oxide formation is suppressed, interfaces are clean, and a single cube-on-cube epitaxy is observed. While the Cu/TiN and TiN/MgO interfaces are rough, the MgO and LaMnO3 layers planarize the material, leading to growth of smooth YBa2Cu3O7−δ (YBCO). Residual strain in the YBCO film is 0.25% or less and does not lead to apparent cracking. The superconducting properties of the samples were investigated by electrical transport and magnetization measurements. For the first time, high critical current density (Jc) values are reported for YBCO films grown on (001) single-crystal and 100‹100›?textured Cu surfaces without intervening metal coatings. Jc on single crystal-like substrates is as high as 3.5 MA/cm2. Reduced Jc of approximately 1 MA/cm2 on rolled Cu tapes is limited by damage to the tape surface during the rolling process.

The analysis of the mixing processes involving water masses on the Ross Sea continental shelf is one of the goals of the CLIMA project (Climatic Long-term Interactions for the Mass balance in Antarctica). This paper uses extended Optimum MultiParameter analysis (OMP), which is applied to four datasets collected during the cruises of 1994/95, 1995/96, 1997/98 and 2000/01 in the Ross Sea (Antarctica). Data include both hydrological, (temperature, salinity, and pressure; T, S, and P, respectively) and chemical parameters (O2, Si(OH)4, PO4, and NO3+NO2). The OMP analysis is based on the assumption that the mixing is a linear process which affects all parameters equally so that each sample shows physical/chemical properties that are the result of the mixing of some properly selected Source Water Types (SWTs). OMP thus evaluates the best set of contributions by all SWTs to each sample, and allows the spatial distribution and structure of the water masses in a basin to be evaluated. Ocean circulation may subsequently be inferred by means of a deeper analysis of the spreading of the water mass. In this study, the “real” Redfield ratios observed in the Ross Sea were used to correct the equations referring to the chemical parameters in accordance with the extended version of OMP. The solutions include some physically realistic constraints. The results allow a detailed description of the water mass distribution, validated through comparison with some “canonical” thermohaline characteristics of the Ross Sea hydrology. In particular our results verify the spreading of the HSSW over the entire continental shelf and emphasize the key role it plays in the ventilation of the deep waters outside the Ross Sea. In addition a description is given of the intrusion of relatively warm waters coming from the open ocean and flowing at some specific locations at the continental shelf break.

We investigated the influence of a chemisorbed S template with c(2 × 2) structure on the epitaxial growth of different oxide buffer layers on {100}〈100〉 Ni. The sulfur superstructure spontaneously forms on the Ni surface during the texturing anneal as a consequence of segregation. However, depending on the initial S bulk concentration and/or specific annealing conditions, the S layer can cover less than the entire substrate's surface. We show that an incomplete c(2 × 2) coverage causes degradation of the seed buffer layer texture as compared to the substrate texture. A simple step consisting of an H2S predeposition anneal can be used to control the superstructure coverage and optimize the seed layer texture.

The growth mechanisms of MgB2 films obtained by different methods on various substrates are comparably studied by transport measurements and scanning electron microscopy observations. The analyzed films include those prepared by ex situ postanneal with Tc0 ˜38.8 K and those from in situ anneal with Tc0 ˜24 K. It is clearly observed that the films obtained by the high-temperature reaction of e-beam evaporated B with Mg vapor are formed by the nucleation of independent MgB2 grains at the film surface, indicating that this approach may not be suitable to obtain epitaxial films. A significant oxygen contamination was also present in films obtained from pulsed-laser-deposition-grown precursors, which drag the Tc0 down to 24 K.

Power applications of high-temperature superconducting (HTS) coated conductors will require stabilization against thermal runaway. We have developed conductive buffer layers to electrically couple the HTS layer to the underlying metal substrate. The structure comprises the layer sequence of SrRuO3 (SRO) on LaNiO3 (LNO) on biaxially textured Ni substrates. We report baseline investigations of compatibility of SRO/LNO multilayer structure with processing of Yba2Cu3O7−δ (YBCO) and demonstrate biaxially textured YBCO films on conductively buffered Ni tapes. These YBCO coatings exhibit self-field Jc values as high as 1.3 × 106 A/cm2 at 77 K, and the entire structure (HTS + conductive buffers + metal substrate) shows good electrical connectivity. These results demonstrate that SRO/LNO buffer layers may provide a basis for stabilized coated conductors.