Homogeneous solution for Y-Ba-Cu-0 superconductor was prepared from yttrium i-propoxide, barium i-propoxide, and copper ethylhexanoate. The solution was converted to a resin-like material and was readily dissolved in organic solvents. The resin possesses a cohesive property in a number of solvents, such as benzene and xylene. Single-phase superconducting YBa2Cu307_x fibers have been continuously spun from the viscous solution. Controlled amounts of Y2BaCu05 phase in the fibers were made possible by slight adjustments in the solution compositions. Partial substitution of copper ethylhexanoate with copper trifluoroacetate prevents barium carbonate formation In the fiber during curing and organic pyrolysis.

Aggregation of YBa2Cu3O7‐x powder by compaction molding and sintering results in porous ceramic with poor mechanical properties and hence improving the ceramic properties using continuous stainless steel fibers have been studied. Fiber reinforced beam specimens (2% of fibers by weight) were prepared by modifying the standard processing method. Fibers were pretreated with silver to reduce the contamination of the superconducting matrix. The mechanical and electrical properties of the superconducting ceramic‐fiber composite was evaluated at 77K. Continuous stainless steel fibers improved the performance of the superconducting ceramic.

A novel rapid densification technique for fabrication of bulk shape YBa2Cu307–xsuperconductor is presented. The Ceracon process is a one‐step, quasi‐isostatic consolidation route utilizing conventional P/M equipment and set‐up. The Ceracon technology has enabled successful fabrication of bulk, shapes such as discs, cylinders, hollow cylinders and spheres along with significant increases in the density up to 95‐98% of the theorertical. The superconducting volume fraction is preserved due to short hold times at the operating temperatures and avoidance of high processing temperatures. Results based on densities, microstructure, susceptibility measurements, X‐ray diffraction patterns and TGA measurements are discussed.

The laser ablation technique was used to fabricate high Tc superconducting composite structures. The multilayered structures were fabricated in‐situ by changing the target during deposition. Thin MgO films and yttrium‐stabilized Zr02 films were used as buffer layers. The composite films were successfully fabricated on ZrO2(100) substrates. There is negligible interdiffusion occurring at the interfaces and the Jc at 77K is higher than 105A/cm2 for YBCO films in a triple layered structure.

Bulk YBa2Cu3O7‐x (YBCO) wires and tubes were fabricated by an extrusion technique. Critical current density (Jc) was measured as a function of applied magnetic field at 77 K and was found to decrease significantly in fields below 100 G. Jc was dependent on specimen geometry. In addition, when a concentric magnetic field was generated by passing a current though a copper wire, the external field from the wire could interfere constructively or destructively with the magnetic field produced by current in a YBCO tube. The change in electrical properties with magnetic field has been attributed to weak‐link behavior at the grain boundaries. Batch‐to‐batch differences in the field dependence of Jc imply the possibility of reducing the dependence by processing modifications.

Conductor development is one of the major long term goals in high temperature superconductor research. In this paper we report on two promising processing technologies that have been utilized to produce superconducting HTS conductors. First, melt spun YBa2Cu3O7 fibers rapid thermal processed for 1‐8 sec at 950 to 1075°C have Tc's to 92 K, Jc's to 1100 A/cm2 and the orthorhombic twinned morphology typical for high quality YBa2Cu3O7 A processing matrix of time, temperature and composition for these fibers shows that slightly CuO‐rich starting compositions give the best results. Second, silver tube encapsulated wires of Bi1.7Pb0.3Sr2Ca2Cu3O10 have been made by extrusion, wire drawing and cold rolling. The resulting tapes show orientation of the crystallites, zero resistance up to 100K and improved magnetic hysteresis above 50 K. The combination of mechanical reprocessing and extended thermal anneals near 850°C appears to significantly improve these materials.

The results of measurements of the transport properties of high‐Tc superconductors containing different amounts of silver are reported. The Tc and Jc values were found to be similar to that of the single phase YBaCuO compound whereas the electrical and thermal conductivities above Tc were drastically increased. A very low contact resistance was observed.

The steady‐state flow stress of YBa2Cu3O7‐δ containing 15 to 30 vol.% Ag has been measured in air at nearly constant compressive strain rates between 5 x 10‐6 and 1 x 10‐4 s‐1 from 830 to 900°C. Addition of Ag dramatically decreases the flow stress compared to that of the pure superconductor, but the stress exponents and the activation energy for deformation remain unchanged.

High‐T YBaCuO and BiSrCaCuO Superconducting wires have been fabricated by powder metallurgy technique. Copper and silver tubes were used as the external jackets. Thermal annealing treatments for all the wire‐type samples were performed between 773 K and 1223 K. Both electrical and magnetization studies show that the superconducting properties can be improved after properly thermal annealing these samples with silver jacket. Our experimental results show that proper thermal annealing treatment can enhance the intragrain critical current density more than 100 times; however, the intergrain critical current density improves only a few times.

Strongly c‐axis textured layers of YiBa2Cu307_x were prepared by sintering a precursor powder on Ag‐foils. Critical current densities of layers with a few (Am thickness are presently jc ∼ 5000‐8000 A/cm2 (77 K, H = 0) over a few centimeters length.

Silver diffuses into the lattice of YBa2Cu307 during the annealing of silver contacts at 500°C. Depth profiles using Auger electron spectroscopy, with a focused electron beam, show an extensive diffusion zone, as well as segregation of barium and oxygen to the surface of the contact. There appears to be a slight loss of silver from the surface region, which could be explained by enhanced concentration at grain boundaries. High resolution SEM analysis of a fracture surface did not reveal the presence of silver on the grain boundaries. Diffusion rates were correlated with grain orientation by using magnetically aligned samples, and were found to be greater for the direction parallel to the C axis.

Preforms made by filling silver tubes with YBa2Cu3O7‐x (YBCO) powder were drawn to obtain wires with diameters in the 0.25mm to 1.00mm range. Straight samples of these wires were sintered and oxygenated. The observed changes in Tc and Jc while the samples were thermaly cycled or mechanically deformed are reported.

Superconducting properties and microstructures of the YBa2Cu3AgxO7‐δ composites have been studied as a function of silver content, 0 ≤ x ≤ 6, using a variety of techniques.The superconducting transition temperature,Tc, of these composites was found to be the same, ∼ 90 K, for the above range of compositions. The composites with x > 3 are found to have resistivity behavior identical to silver metal above the superconducting transition temperature. The peritectic transformation temperature of the 123 material in the composite is lowered. Alloy formation between Ag and Cu is proposed to take place triggering the peritectic transformation at lower temperatures. The silver is observed in the form of precipitates at very low concentrations of silver, indicating that silver does not substitute for copper in YBa2Cu3AgxO7. Lattice parameters of the composites were found to be invariant throughout the above composition range. The addition of Ag2O in the starting composition seems to stabilize the stoichiometric YBa2Cu3AgxO7 by way of decomposition to Ag and O, also, the better diffusion of oxygen through silver in comparison with that through the superconductor helps the regeneration of superconductivity in the composite superconductor. As a result, the incorporation of oxygen and recovery of superconducting properties is enhanced in the silver composites.For values of x > 3 small quantities of 211 phase were detected along the grain boundaries, which makes the residual composition poor in copper resulting in the formation of non‐superconducting 211 phase.

Silver is known to act as a compatible metal host for designing a microcomposite system with the high temperature superconducting ceramic YBCO[l,3]. The unique role played by nascent silver generated from the silver monoxide precursor during sintering as well as warm compaction of the powder mix is illustrated with the help of light optical micrography. It is seen that electrical as well as mechanical properties of the bulk composite is significantly governed by its microstructure. The microstructure, in turn, could be controlled by suitable heal treatment and proper selection of the fabrication process parameters at every step. Attempting a structure‐propcrty‐processing correlation, a microstructure controlled scheme for fabricating superconducting composite product of useful shapes is discussed. Successful fabrication of thin (0.75 mm dia.) and long (450 mm) flexible wire following this route is also reported here.

Magnetic shields for SQUID applications were successfully fabricated using high Tc superconducting BSCCO. To produce shields with appropriate superconducting properties and close dimensional control, it was necessary to develop new processing techniques. Shields were produced by casting liquid BSCCO into molds, heat treating and machining. This technique is applicable to fabricating other types of superconducting devices requiring bulk superconductors with complex shapes and close dimensional control.

Au‐Sheathed Y‐Ba‐Cu‐O(YBCO) and Tl‐Ba/Sr‐Ca‐Cu‐O(TBSCCO) tapes were fabricated by the drawing‐rolling and subsequent unidirectional solidification. A typical microstructure of melt‐textured polycrystallite including fine particles of second phase(e.q. Y‐211) was observed. The Tl‐2223 tapes prepared at an optimized condition yielded Jc=15,300 A/cm2 at 77K in the absence of magnetic field, and l,100A/cm2 in a magnetic field of IT. The enhancement of Jc in a magnetic field is suggested to be due to the improvement of weak‐links in grain boundaries.

A series of 4336 Bi‐Sr‐Ca‐Cu oxide samples doped with 1 to 5% metallic Ag was prepared by solid state reaction. The distribution of Ag, the microstructure and the crystal structure of the samples were studied using energy dispersive spectrometry, EDS, scanning electron microscopy, SEM, and x‐ray diffractometry, XRD. Addition of Ag leads to a marked increase in preferred orientation with (001) planes perpendicular to the pressing direction in sintered pellets. The resistivity‐temperature data show an enhanced Tc in Ag‐doped samples under certain conditions. Energy dispersive spectrometry indicates that the dopant mostly segregates to the grain boundaries.

We have studied phase evolution in Ag‐clad BSCCO wires with nominal composition Bi2.4.8Sr2.05Ca0.95Cu2.27Oy‐ The wires were initially processed at 920°C where the oxide was partiaily moiten, then subsequently annealed at 840° C. The microstructure and composition of the phases present were studied at different points in the processing using optical and scanning electron microscopy, and electron probe microanalysis. The microstructure became simpler during the anneal resulting in two oxide phases and Ag. Ag from the cladding had dissolved into the melt at 920° C and subsequently precipitated in the core of the wire on cooling to the annealing temperature.

A study of magnetic field trapping phenomenon in oriented grain YBa2Cu3O7‐x samples produced by liquid phase processing has been conducted. The magnetic field reproduced from the parent magnetic field allows the production of “magnet replicas”, which can be used in various instruments when large magnetic field is needed constant in time. This paper reports the magnetic field trapping capability and uniformity observed in these oriented grain samples. The feasibility of building large and uniform magnetic field by assembling small SC specimens has also been explored.

A novel chemical etchant for the high temperature superconducting material YBa2Cu3O7‐x is demonstrated. The etching solution which consists of ethylenediaminetetraacetic acid (EDTA) in water does not degrade the properties of the superconducting films and is suitable for applications with standard photolithography. We have etched 2‐200 μm wide wires which show no degradation of Tc ( within 1 K accuracy of the measurements) and show zero‐resistance temperature ≥90 K. The etchant exhibits a polishing effect by selectively removing the porous and semiconducting surface layers which are formed during high temperature annealing process. The dense bulk of the films are etched at a rate of 1400 Å/min which provides control for fine‐line patterning of thin film material. The critical current densities of the unpatterned films which are polished by reactions with EDTA remain unaffected and are measured to be about 5 x 106 A/cm2.