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A new approach for the deposition of layers for coated conductors has been developed. High-frequency surface acoustic waves (SAWs) were applied for the atomization of precursor solutions into an ultrafine aerosol. The deposition via aerosol droplet condensation offers several advantages over existing deposition methods including ink jet printing and dip coating, e.g., a variable droplet size and the possibility of gel condensation in the aerosol phase due to solvent evaporation. In the future, a combination of two or more SAW atomizers might enable the simultaneous deposition of separate solutions and even nanoparticle dispersions. First, experiments were performed using water-based and propionic-acid-based mixed lanthanum and zirconium precursor solutions. These solutions are supplied to a SAW device via a stainless steel capillary, leading to continuous aerosol production. The aerosol droplets of the precursor solution were deposited on biaxial textured Ni-5 at.%W tapes having an area of 1-cm width and about 5-cm length and were subsequently crystallized into a continuous thin La 2 Zr 2 O 7 buffer layer in a tube furnace. X-ray diffraction studies showed that the La 2 Zr 2 O 7 films have high crystalline quality with a strong (001)-orientation. Furthermore, microstructural analysis on the deposited films showed homogeneous and dense layers.

Ion Beam Assisted Deposition (IBAD) offers the opportunity to prepare highly textured templates for YBa2Cu3O7-δ (YBCO) coated conductors. We investigated a new simplified buffer layer architecture on mechanically polished stainless steel tapes with an amorphous Ta0.75Ni0.25 bed layer. Cube textured TiN layers have been prepared by ion beam assisted pulsed laser deposition on these substrates. Consequently, highly textured YBCO layers were obtained with an (103) in-plane alignment of Δφ = 5.9° using an additional SrZrO3 buffer layer. A maximum critical current density of about 2.9 MA/cm2 was measured at 77 K in self-field. The films showed an improved Jc(H)-behavior compared to standard YBCO coated conductors.

Ion beam assisted deposition (IBAD) was used in combination with pulsed laser deposition to develop a conductive biaxially textured buffer architecture based on IBAD-TiN for coated conductor applications. Highly textured TiN layers were prepared on Hastelloy substrates with an amorphous Y2O3 seed layer. The cube textured nucleation layer was preserved to higher thicknesses using homoepitaxial growth. A double layer of Au and Ir was used to reduce the lattice misfit between TiN and YBCO. Finally, a 120 nm thick Nb:SrTiO3 layer was deposited to ensure the epitaxial growth of the superconducting YBCO layer at higher oxygen pressures. In-situ RHEED measurements revealed an undisturbed epitaxial growth of the complete buffer layer stack. The buffered tape was successfully used for the deposition of a 300 nm thick YBa2Cu3O7-x layer, showing an in-plane FWHM value of 7.2deg and a critical temperature T c of about 88 K. The results are promising for the development of a completely electrical conductive buffer architecture based on the IBAD approach.

A procedure is developed for assessing the epitaxy of La2- xZr2+ xO7 (LZO) layers on NiW RABITS. Comparing XRD patterns ( thetas -2thetas scans and 2D rocking curves) of LZO films of known thickness (ellipsometry or reflectometry measurements) with those of standard samples (100% epitaxial LZO film and an isotropic LZO pellet of known density), we estimate the epitaxial (EF), and polycrystalline (PF) fractions of LZO within the layer. The procedure was tested using MOD-LZO(100 nm)/NiW tape samples with EF varied from 3 to 90% (reproducibly prepared by varying the humidity of Ar - 5%H2 gas during heat treatment). A qualitative agreement with RHEED and quantitative (within plusmn 10%) agreement with the EBSD results was shown. Correlation between EF and J c in 600 nm thick YBCO layer deposited on MOD-LZO/NiW using thermal coevaporation enables us to impose the EF = 80% margin on the quality of LZO layer for the particular conductor architecture.

The critical current density Jc is limited by the network of small angle grain boundaries in coated conductors based on biaxially textured metal substrates up to a texture dependent cross-over field. Below this cross-over field Jc can be improved by optimizing the grain boundary network. One possibility to enhance Jc at low magnetic fields is to use substrates with high aspect ratio grains. Therefore, cube textured Ni tapes micro-alloyed with silver were prepared having such an elongated grain structure with an aspect ratio of about 4. Highly textured NiO layers have been grown on these substrates using surface oxidation epitaxy (SOE). YBCO films were deposited afterwards on these substrates by pulsed laser deposition using a BaZrO3/SrRuO3 buffer layer architecture. Transport measurements revealed a significant enhanced Jc value along the rolling direction of the tape compared to the transverse direction. Similar results were obtained in numerical simulations based on measured EBSD texture maps.

The preparation of cube textured NiO buffer layers on biaxially textured Ni tapes using surface oxidation epitaxy (SOE) offers a cheap and scalable route for the production of long-length YBCO coated conductors. A second buffer layer is necessary to ensure epitaxial growth of the YBCO as well as to prevent Ni contamination of the superconducting layer. Zirconate buffer layers offer a close lattice misfit to NiO as well as a high stability during the YBCO deposition. BaZrO/sub 3/ and SrZrO/sub 3/ buffers were successfully deposited on NiO using pulsed laser deposition. Additionally, BaZrO/sub 3/ films were prepared on NiO using metal-organic decomposition. All buffers show a high quality epitaxial growth with an in-plane orientation similar to the underlying NiO. The subsequent deposition of YBCO on top of these buffers resulted in epitaxial layers with a T/sub c/ above 85 K and j/sub c/ up to 1 MA/cm/sup 2/ on NiO if a thin intermediate SrTiO/sub 3/ layer is used. Microstructural investigations showed that the roughness and the surface topography of the buffer layers is mainly determined by the quality of the NiO layer.

The critical current density in RABiTS (rolling assisted biaxially textured substrates) based coated conductors is limited by the network of small-angle grain boundaries up to a texture dependent crossover field H/sub co/. The current flow through this network is percolative in nature and thus depends on misorientation angle distribution, the width and length of the tape, and on the grain shape. These dependencies were simulated using a fast and simple limiting path algorithm on real grain boundary networks obtained by electron backscattering diffraction (EBSD) and cross-checked with transport measurements. A strong dependence of J/sub c/ on conductor width below 20 grains and a large increase in J/sub c/ for elongated grains was found. H/sub co/ of tapes with very sharp cube textures are around 1 T at 77 K. Hence, the intra-grain pinning must be increased for a further improvement of coated conductors applied in higher magnetic fields. With transport measurements on YBa/sub 2/(Cu/sub 1-x/Zn/sub x/)/sub 3/O/sub 7-/spl delta// single crystalline thin films, the possibility of a J/sub c/ increase due to Zn doping was investigated. Monolayer films with Zn contents up to 0.2%, however, showed a decrease in J/sub c/ and H/sub irr/, whereas multilayer films with x=0.017% and x=0.025% Zn) showed an increase in J/sub c/ at 77 K.

By using a simple single-pass reel-to-reel system, we demonstrate a simple and robust in-situ route for the continuous deposition of 1-2 m long Coated Conductors (CC) consisting of 1 /spl mu/m thick superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) films deposited by thermal co-evaporation onto 100 nm thick CeO/sub 2/ buffered cube textured Ni tapes. The buffer layer was deposited by either e-beam or thermal evaporation using respectively ceria or metallic cerium. The structural and morphological properties of the samples were investigated by X-ray /spl thetav/-2/spl thetav/ Bragg-Brentano, and pole figure diffraction, Nomarsky optical microscopy and Scanning Electron Microscopy (SEM) analysis. The 123 composition was controlled during deposition by means of an atomic absorption system. The optimized buffer layer and YBCO layer are grown at 690/spl deg/C in respectively forming gas and oxygen partial pressures of 5/spl times/10/sup -5/ mbar. These conditions ensure the growth of dense and crack-free layers with good biaxial texture, as indicated by FWHM's values in the 5-7/spl deg/ range for both in- and out-of-plane orientations. Zero-resistance critical temperatures T/sub c/=86-87 K with transition widths /spl Delta/T/sub c/

We present a noninvasive inductive analysis of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) IBAD (ion beam assisted deposition) and RABiTS (rolling assisted biaxial textured substrates) coated conductors that enable us to analyze the electromagnetic granularity effects. We distinguish flux penetration through grain boundaries and grains and determine the inductive intergranular critical current density. The signature of reverse flux at low angle grain boundaries has been clearly identified by the appearance of a peak in the return branch of the irreversible magnetization. The present analysis evidence that IBAD and RABiTS coated conductors may exhibit comparable inter-grain critical current densities with the determining factor being the average in-plane grain misorientation.

Superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films were prepared via chemical solution deposition (CSD) in a trifluoroacetate (TFA) process. The dip coated substrates were treated in a two stage annealing process. We obtained epitaxially grown 190 nm thick films on single-crystalline strontium titanate with T/sub c/ of 89.9 K and a transition width of 0.7 K. Critical current densities up to 4 MA/cm/sup 2/ were reached. The interface between the substrate and the YBCO is sharp even on an atomic level. Biaxially textured strontium titanate films and ytterbium oxide films as buffer layers were also built in a TFA process on single-crystalline substrates. Biaxially textured CeO/sub 2/ buffer layers were deposited on nickel RABITS using a nonfluorine precursor.

The grain boundary (GB) network in biaxially textured YBa/sub 2/Cu/sub 3/O/sub x/ (Y123) coated conductors is the key to their transport properties and determines the upper limit for the critical current density. In this contribution we report on detailed EBSD (electron backscattering diffraction) investigations of the formation of these GB networks in Y123 films deposited on highly biaxially textured metallic substrates and the comparison of the measured critical current density with simulations based on the exact knowledge of the underlying GB network. Highly cube textured Ni-tapes were prepared by rolling and recrystallization and detailed texture maps were determined by EBSD before and after the deposition of Y123 films by thermal evaporation or pulsed laser deposition. This allowed the quantitative evaluation of both the Y123-growth on different oriented Ni-grains and the GB misorientation network which determines the critical current density. This exact texture information was also used to calculate the critical current density based on the well known exponential j/sub c/-dependence across Y123 tilt GBs and is compared to the measured transport j/sub c/ across the same substrate area.

Highly cube ({001} ) textured Ni- and Ni-alloy tapes are produced by heavy cold rolling and recrystallisation annealing. Due to impurities in Ni, abnormal grain growth destroying the cube texture often occurs at temperatures above 600/spl deg/C. This could be prevented by alloying Ni with 0.1 at.% of different elements each leading to a texture improvement with increasing annealing temperature. YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//-films deposited on these tapes reach critical current densities up to 0.5/spl times/10/sup 6/ A/cm/sup 2/. Also Ni-Cr and Ni-V were successfully processed to highly cube textured tapes. Their magnetic and mechanical properties were characterized. Ni-13 at.% Cr and Ni-11 at.% V have a Curie temperature below 77 K. Their yield strength is three times higher than that of unalloyed Ni.

MgB2 single-filament tapes and wires with Monel/Nb sheath were produced by the Powder in Tube (PIT)-technique using MA in-ex situ powder. This powder prepared by mechanical alloying (MA) of Mg and B was finally reacted to MgB2 at 700°C. The amount of MgB2 after annealing was about 91 wt%. Additionally 9 wt% MgO secondary phase was found. The primary crystallite size was about 25 nm. Critical current density measurements have shown relatively high values of Jc = 104 A/cm2 at 6.7 T for unsintered tapes in parallel magnetic field. Heat treatment at temperatures of up to 900°C could not improve these values, probably due to MgO hindering the sintering process.

Using Ion-Beam Assisted Laser Deposition (IBALD), biaxially oriented films of Yttria stabilized Zirconia were deposited on polycrystalline and amorphous substrates. The film texture in dependence of deposition parameters was examined with X-ray texture analysis. As deposited films were analyzed by transmission electron microscopy and atomic force microscopy. All films showed a columnar film growth structure. The diameter of the columns increased with film thickness and could be related to the film in-plane orientation. The nucleation process was found to be polycrystalline and independent of the ion-beam assistance. At an early growth stage, a growth structure of [001] oriented columns emerges from the randomly oriented crystallites. The film in-plane texture forms in a competition of [001] oriented columns, where columns oriented with their [111] axis parallel to the impinging ion-beam dominate the film texture. The out-of plane growth orientation was found to depend on substrate temperature and laser energy density, while the ion-beam affects mainly the in-plane orientation.

For the preparation of MgB2 precursor powder the technique of mechanical alloying was applied. Tapes with Fe- and Cu/Nb-sheath have been prepared by the powder-in-tube method using these nanocrystalline precursor powders consisting of Mg, B and during the high energy milling reacted MgB2. Differences in the quality of the boron powders used for the preparation of MgB2 powders have a distinct influence on mi- crostructure and superconducting properties of bulk samples and tapes. The high density of grain boundaries acting as pinning centers enhances the critical current density Jc up to 104 A/cm2 at fields of about 5 T (20 K) and 10 T (4.2 K) in Fe-sheathed tapes. The effect of nanoparticle additions like SiC and WC on the mi- crostructure and critical currents of bulk samples and tapes is discussed.

The stability and corrosion of highly coercive and highly textured Nd-Fe-B films is examined. The rapid degradation of coercivity within hours after deposition and the relatively slow reduction of remanence and magnetic texture together with depth profile analysis show that oxidation of the Nd-rich intergranular phase is the first step of corrosion. Consequences on coercivity are discussed together with a reduction of the local anisotropy field at the surface. For applications of thin Nd-Fe-B films degradation can be inhibited by covering with a Cr protection layer.

Hard magnetic Nd-Fe-B and Sm-Co films have been deposited on various substrates with a Cr buffer layer. The morphology of the buffer was modified from a smooth to a rough, meander-like structure. Films deposited on the rough buffers exhibit a significantly higher coercivity. The feasibility of Cr as a diffusion barrier and as an intermediate layer to induce magnetic texture in these systems is discussed.