Prior to the 9th International Conference on Reactivity Solids in Krakow, Poland a group of about 25 international scientists held a special conference entitled "Transport in Nonstoichiometric Compounds" in late Aug. 1980 in Mogilany, Poland (near Krakow). This conference was well received in view of the interaction between the participants, as well as the resulting publication of the proceedings (Elsevier Scientific Publishing Company, 1982, edited by J. Nowotny). At this first conference the participants decided that it would be desirable to organize similar conferences at about two year intervals. Thus, a second meeting was held in late June, early July at Alenya, Pyrenees Orientales, France. This conference had a larger number of participants, about 50, but still managed to promote excellent interaction between all the participants. These proceedings, with editors G. Petot-Ervas, Hj. Matzke and C. Monty, have also been published by Elsevier as a special edition of the journal, Solid State lonics, Vol. 12 (1984). In view of the success of the initial two conferences, a third meeting was organized and held at The Pennsylvania State University, University Park, PA., 16802, U.S.A. from 11 June 84 to 15 June 84. The proceedings of this conference are presented in the following text.

The material in this book is based on invited and contributed pa pers presented at the NATO Advanced Research Workshop on INon-stoichio l metric Compounds held in Ringberg Castle, Rottach-Egern (Bavarian Alps), Germany, July 3-9, 1988. The workshop followed previous meetings held in Mogilany, Poland (1980), Alenya, France (1982), Penn State, USA (1984) and Keele University, UK (1986). The aim of these workshops is to present and discuss up-to-date knowledge in the study of non-stoichiometry and its effect on materials properties as well as to indicate the most urgent research pathways required in this field. Since the subject of non-stoichiometry is interdisciplinary, the workshops bring together solid state physicists and chemists, surface scientists, materials scientists, ceramists and metallurgists. The present workshop, which gathered 42 scientists of an inter national reputation, mainly considered the effect of surfaces, grain boundaries and structural defects on materials properties. From discus sions during this meeting it emerged that correct understanding of properties of ceramic materials requires urgent studies on the defect structure of the interface region. Progress in this direction requires the development of the interface defect chemistry. This is the task for materials scientists in the near future. The present proceedings includes both theoretical and experimen tal work on general aspects of non-stoichiometry, defect structure and diffusion in relation to the bulk and to the interface region of such materials as high tech ceramics, solid electrolytes, electronic cera mics, nuclear materials and high Tc oxide superconductors.

Nonstoichiometric Oxides discusses the thermodynamic and structural studies of nonstoichiometric oxides. This eight-chapter text also covers the defect-defect interactions in these compounds. The introductory chapters describe the thermodynamic properties of nonstoichiometric oxides in terms of defect complexes using the classical thermodynamic principles and from a statistical thermodynamics point of view. These chapters also include statistical thermodynamic models that indicate the ordered nonstoichiometric phase range in these oxides. The subsequent chapters examine the transport properties, such as diffusion and electrical conductivity. Diffusion theories and experimental diffusion coefficients for several systems, as well as the electrical properties of the highly defective ionic and mixed oxide conductor, are specifically tackled in these chapters. The concluding chapters present the pertinent results obtained in nonstoichiometric oxide structural studies using high-resolution electron microscopy and X-ray and neutron diffraction. Inorganic chemists and inorganic chemistry teachers and students will greatly appreciate this book.

One of the fundamental objectives of physical geochemistry is to understand the evolution of geochemical systems from microscopic to regional and global scales. At present there seems to be a general recognition of the fact that internal properties of minerals record important aspects of the evolutionary history of their host rocks which may be unraveled by very fine scale observations. A major focus in the development of geochemical research in the last thirty years has been the application of classical thermodynamics to reconstruct the conditions at which the states of quenched mineralogical properties of rocks have equilibrated during the course of their evolution. While these works have funda mentally influenced our understanding ofthe physico-chemical history ofrocks, in recent years petrologists, mineralogists, and geochemists have been making greater efforts towards the application of kinetic theories in order to develop a better appreciation of the temporal details of geochemical processes. The present volume brings together a variety of current research on transport in systems of geochemical interest from atomic to outcrop scales. A major theme is atomic migration or diffusion, and its various manifestations on microscopic and macroscopic scales. Transport in the solid state is controlled by diffusion and is responsible for the states of atomic ordering and relaxation of composi tional zoning in minerals, development of compositional zoning during cooling, exsolution lamellae, and creep.