The field of high-temperature superconductivity has encouraged an inter disciplinary approach to research. It has required significant cooperation and collaboration among researchers, each of whom has brought to it a rich variety of experience from many other fields. Recently, great improvements have been made in the quality of research. The subject has matured and been launched into the next stage through the resonance between science and technology. The current progress of materials processing and engineering in this field is analogous to that previously seen in the development of semiconductors. These include the appearance of materials taking the place of YBa2Cu307 owing to their improved properties (higher critical temperatures and stronger flux pin ning) in which rare earth ions with large radii (La, Nd, Sm) substitute for Y; the development of technology enabling growth control on the nanometer scale; and precise and reproducible measurements that can be used as rigorous tests of theoretical models, which in turn are expected to lead to the develop ment of new devices. For further progress in high-T research, academics and c technologists must pool their knowledge and experience. I hope that this volume will promote that goal by providing the reader with the latest results of high-temperature superconductor research and will stimulate further discussion and collaboration.

Since the discovery of superconductivity with trans1tton temperatures above 77 K, concentrated research activities toward the exploration of practical applica tions of these materials have been carried out. Currently, a remarkable improve ment in superconducting properties has been achieved due to the fine optimization of fabrication processes, and this has attracted industrial interest for future applications. In the case of NdBa Cu 0 materials, a new pinning mecha 2 3 7 nism was found which enhances the critical current under applied magnetic fields. In single crystals of these materials, oxygen control results in an increase in the growth rate. The metalorganic chemical vapor deposition (MOCVD) film quality has been improved by using a new liquid raw material. Simultaneously, real demands from the viewpoint of the market start to be a motivation force, es pecially in electronics application where some products are already being sold. At the same time, interesting physical properlies have been obtained from a new superconducting single crystal which has a layered perovskite structure without copper. In addition, various precision measurement techniques have confirmed the d-wave mechanism and the existence of intrinsicJosephson junctions in single crystals. These new phenomena challenge the existing theoretical models but also open the way for new applications. These significant areas of progress in materials science have led high-Tc super conductivity research into the next phase of activity, while fundamental research continues to be very important. I sincerely hope that this volume will give further impetus to this development.

The 11th International Symposium on Superconductivity was held November 16-19, 1998, in Fukuoka, Japan. Convened annually since 1988, the symposium covers the whole field of superconductivity from fundamental physics and chemistry to new applications. At the 11th Symposium, there was increased interest reported in the development of trial devices using bismuth wires and yttrium-based bulk materials. Among the presentations were those that clearly defined the development targets for next-generation yttrium-based wires and bulk materials and single-flux quantum (SFQ) circuits. Other popular topics were high-temperature superconductivity applications such as SQUIDs, microwave filters, and cryocooler-cooled magnets. With more than 600 participants from 18 countries, the symposium provided an excellent forum for exchanges of the most recent information in the field of superconductivity.

The International Symposium on Superconductivity, which has been held annu ally since 1988, is a forum for presenting the most up-to-date information about a broad range of research and development in superconductivity, from funda mental aspects to applications. More than 10 years have passed since the discovery of oxide superconductors and since various developments of applications began. It may be said that the prospects for application of oxide superconductors recently have opened up. Great progress has been made toward practical use, for example, of the flywheel, which uses bulk materials, and the high-performance cryo-cooled magnet made of bismuth wire. These were the results of persistent efforts to develop materials from the viewpoint of materials science and engineering. Also important is the progress in comprehensive understanding of high temperature superconductivity. Unique electronic properties of cuprates such as the non-Fermi liquid normal state, spin-charge separation, spin gap, and d-wave symmetry were discussed at the symposium, as were the unique electromagnetic properties resulting from the low dimensionality of cuprates. In the field of new superconductors, many exotic materials have been discovered since 1986. A decade of work with cuprate superconductors is reviewed in this proceedings, and several of the newest materials are presented. These papers will be instructive for many researchers and for students who are to enter this field.

This volume contains the proceedings of The Second Polish-US Conf- ence on High Temperature Superconductivity which was held August 18-21, 1998 in Karpacz, Poland. The conference followed The First Polish-US C- ference on High Temperature Superconductivity organized in 1995, proce- ings of which were published by Springer-Verlag in 1996 (Recent Devel- ments in High Temperature Superconductivity, Lecture Notes in Physics 475). High Temperature Superconductivity (HTSC) in complex copper oxides has become a household name after twelve years of intense research following its discovery in 1986 by J. G. Bednorz and K. A. Miiller. Because of the rapid growth of the HTSC field, there is a need for periodic summary and conden- tion both for scientists working in the field and, especially, for young resear- ers entering the field of oxide materials. Following the First Conference, it was recognized that an extended format of lectures perfectly satisfied that need, providing adequate time for experts from the international community to fully introduce and develop complex ideas. Thus, the format of the Second Conference brought together by cooperating scientists from the Institute of Low Temperature and Structure Research of the Polish Academy of Science at Wroctaw, Northern Illinois University, and Argonne National Laboratory remained mostly unchanged. Again, we were delighted to receive enthusiastic responses from distinguished US and Polish scientists who were invited to p- ticipate.

This book presents state-of-the art research on superconductivity which is the ability of certain materials to conduct electrical current with no resistance and extremely low losses. High temperature superconductors, such as La2-xSrxCuOx (Tc=40K) and YBa2Cu3O7-x (Tc=90K), were discovered in 1987 and have been actively studied since. In spite of an intense, world-wide, research effort during this time, a complete understanding of the copper oxide (cuprate) materials is still lacking. Many fundamental questions are unanswered, particularly the mechanism by which high-Tc superconductivity occurs. More broadly, the cuprates are in a class of solids with strong electron-electron interactions. An understanding of such "strongly correlated" solids is perhaps the major unsolved problem of condensed matter physics with over ten thousand researchers working on this topic.

In contrast to research on the fundamental mechanisms of High-Temperature Superconductivity, in recent years we have seen enormous developments in the fabrication and application of High-Tc-superconductors. The two volumes of High Temperature Superconductivity provide a survey of the state of the technology and engineering applications of these materials. They comprise extended original research papers and technical review articles written by physicists, chemists, materials scientists and engineers, all of them noted experts in their fields. The interdisciplinary and strictly application-oriented coverage should benefit graduate students and academic researchers in the mentioned areas as well as industrial experts. Volume 1 "Materials" focuses on major technical advancements in High-Tc materials processing for applications. Volume 2 "Engineering Applications" covers numerous application areas where High-Tc superconductors are making tremendous impact.