While high Tc superconductivity was first discovered in bulk material, it was apparent that thin films of these materials, particularly the compound YBa2Cu3O7-δ, would be of great interest to both science and technology. In this sense the development of these materials parallels a similar history in the low Tc materials. Initially, most of the low Tc materials of interest were single element metals such as Nb, Pb and Al in bulk form. Later work, mostly in magnets, led to the development of compounds or alloys of such metals as Nb-Sn, Nb-Ti, and many others. However, many physical and technological investigations required thin films with thicknesses in the range of 0.1-10μm. Microwave, infrared, and critical current studies are examples of some of the scientific uses of thin films. A few examples of the applications would include josephson junction-based digital computer circuits, SQUID (Superconducting Quantum Interference Devices), transmission lines, and interconnects and rf mixers. These studies are also of great interest in the high Tc materials. It is readily apparent that scientific and technological developments in superconductivity are closely interwoven.

The high level of interest in thin films can be appreciated by observing that it was barely a few months after the announcement of superconductivity above 77 K that the first films of these complex, multi-element materials, superconducting at about 86 K were announced. These early efforts at thin film fabrication were generally accomplished using multi-element deposition techniques but subsequent development has seen many varieties of film fabrication techniques used quite successfully to fabricate high-quality films.

The State University of Mons was established in 1965, at the heart of an old industrial region of South Belgium. Since that time, the role of the University emerged as a source of new ideas for the region. The Department of Materials was founded in 1988, developing from the identification of various groups and their expertise in the materials science field. The goal of the Department of Materials is “to arrange and promote researches in this field. The Department will also work at improving education in Materials Science.” The Department will continue existing contacts and promote new contacts with regional, national, and international industries, and its experimental facilities are accessible to all interested researchers.

The members of the Department of Materials belong to the Faculties of Science and Medicine of the State University of Mons. They form an interdisciplinary group, including physicists, chemists and biologists—experimentalists and theoreticians.

Although some research activities involve more than one group, they can be arranged according to either the nature of materials (thin films, polymers, surfaces, quasi-one-dimensional conductors, bio-materials) or methods of preparation (laser irradiation, chemical vapor deposition, electron evaporation) and characterization (electron and x-ray diffraction, spectrophotometry, FTIR, micro-Raman, electrical conductivity, surface analytical techniques).

High Tc oxide superconductors can be prepared by a variety of novel metallurgical or ceramic processing techniques. For example, forming metallic precursors of YBa2Cu3 or REBa2Cu3, where RE is a rare earth element, followed by oxidation has yielded the corresponding ceramic oxide in pellet, wire, and thin film forms. Ceramic fabrication techniques (which often involve incorporating fine particles of the ceramic in a suitable vehicle) such as doctor-blade tape casting and screen printing have been utilized to synthesize both tapes and thin films. Due to intense worldwide effort to develop these ceramics into useable forms, many unique fabrication techniques have been employed, such as the melt-textured growth method of Jin et al. and dynamic compaction. In addition, it is likely that numerous laboratories, particularly industrial, are developing proprietary methods to fabricate wire and other forms but have not published these results due to the intensely competitive nature of this area. In this article, we review some of the methods reported so far for preparing high Tc ceramic superconductors, and we discuss one example of a proprietary method being developed at one of the author's (LDW) laboratories.

Tapes of YBa2cu3O7-x fabricated using the doctor-blade tape casting technique were first displayed by AT&T Bell Laboratories scientists at the 1987 March meeting of the American Physical Society. This method involves mixing ceramic powder, a binder to provide green (unfired ceramic) strength, a plasticizer to provide flexibility, a dispersant to prevent particle agglomeration and a solvent. After mixing all these components together, the solution is poured into a “doctor blade” device which allows a controlled thickness of material to be deposited on a plastic film carrier that passes underneath the doctor blade.

In the analysis of object or material form and structure, especially micro-structure, correlations of material properties with their microstructure, and of structures with their production history and function, are at the heart of much of artifact and fossil analysis in archaeometry. Presently, a great deal of such examination of archaeomaterials is either:

∎ qualitative, descriptive and anecdotal, comparing “representative” specimens to illustrate the differences of mean, typical, or normative structures, and forms; or

∎ limited to measurement of parameters which oversimplify the structure or are easily measured by hand, e.g., length, width, and thickness.

These do not differentiate shape variation or describe irregular shapes effectively. Hand measurements, even simple ones, are often difficult to derive on microstructures or on irregular macroscopic-sized objects and normally involve too few data points for statistical interpretation. Images of tesselated mosaics and multiphase microstructures in materials such as metals or ceramics are often chaotic and irregular in form, size variation and distribution of elements, inclusions and phases. Because of this, they are difficult to quantify precisely or accurately. Moreover, analysis is often limited more by the need to minimize destruction to an irreplacable artifact or art object than by a method's ability to generate significant data. Sample size is often held at the minimum threshold of significance or adequacy. Thus, any method which enhances the quality and quantity of such data should be welcome in archaeometric research.

More than 1,800 scientists from the United States and 33 other countries convened at the MRS Spring Meeting in San Diego, April 24-29,1989 to meet with their colleagues and discuss the latest research on a wide range of topics. According to Meeting Cochair Richard W. Siegel of Argonne National Laboratory, “It was a stimulating, broad-based, interdisciplinary scientific meeting of the high caliber that the materials research community has come to expect from the Materials Research Society.”

Siegel, along with Cochairs Robin EC. Farrow of IBM's Almaden Research Center and Angelica M. Stacy of the University of California led a cadre of 54 volunteer symposium organizers to present an impressive array of leading-edge topics in 17 different symposia, including a late-news technology update on diamond films. Topics ranged from the fundamental condensed-matter physics and chemistry of small atomic clusters, high Tc superconductors, and the processing of a wide variety of optica], electronic, and ceramic materials to the consideration of problems and solutions regarding materials for the world's infrastructure.

Complementing the wide range of scientific interests probed at the Spring Meeting were a three-day exhibit of the latest analytical and processing equipment, and a week-long series of 15 specialty, review, and survey short courses, many directly related to the symposium topics.

There is a widespread feeling that the discovery of high temperature superconductors will force us to change our way of thinking about superconductivity in solids. It has steadily emerged that the simple free-electron picture is inadequate, that a new mechanism of superconductivity is most likely at work, and that modifications (if not outright revisions of the many-body theory) are needed. The situation is not entirely without precedent: much the same could have been said of superfluidity in liquid He. That, however, did not cause such a stir: it had been anticipated some 12 years before its eventual discovery, and the transition temperature of liquid He is so low that experiments have been confined to the few laboratories around the world with a milli-kelvin capability. Finally, the normal state of He was already wellunderstood, so that theorists were poised and ready to tackle the problems posed by the superfluid.

Contrast the oxides. Even the rather extensive earlier studies of Ba1-x PbxBiO3 and other superconducting oxides did not prepare us for the advances of the past two years. Laboratories all over the world have been able to prepare and study the new superconductors rather easily, although well-characterized samples and incisive experiments have not been so easy to come by. The flood of new information poses a particular challenge for condensed matter theory — to distil the essence of these complicated multicomponent materials and to explain how the genie of high temperature superconductivity has escaped after so many years. Despite the existing understanding of the properties of oxides, much work remains to be done before we have a good grip on the many-body theory of these strongly correlated systems.