Among the numerous applications of the rare-earth elements, the field of catalysis accounts for a large number. Catalysis represents approximately 20% of the total market sales of rare earths worldwide. As a matter of fact two main applications have been prominent in the last decades: zeolite stabilization for fluid cracking catalysts, and automotive post-combustion catalytic treatment.

The oldest use of rare earths in catalysis deals with the structural and chemical stabilization of the zeolites for petroleum cracking applications. For a long time this has been an area of application for non-separated rare earths. The addition of several percent of rare earths in the pores of the zeolite results in a strong surface acidity, which is essential for an efficient conversion of high-weight molecules into lighter species, like low-octane fuel, even in the very aggressive conditions of the petroleum industry.

The popular demand for high-quality air in spite of the traffic congestion in large cities resulted in larger and larger constraints in the emission exhaust from cars. Thus highly efficient catalysts have had to be designed, and due to the combination of its redox properties and very good thermal stability, cerium oxide has been since the beginning, early in the 1980s, a major component of the three-way catalysts (TWC) now used in all modern gasoline cars.

The future of rare earths in catalysis is probably bright. The fact that approximately 400 patents are applied for yearly in the area since 1992 is an illustration of a very active area. Usage of rare earths in catalysis is expected to grow due to their highly specific properties. Instead of the physical properties used in electronic applications, one deals now with redox properties, water and thermal stability, coordination numbers and so forth. The rare earths are so specific in these properties that their use can hardly be avoided, not only for the beauty of academic studies but also for the development of industrial applications with immediate influence on everyday life.

Careful control of the synthesis conditions and the definition of optimum composition in each case are the keys to the preparation of highly performing compounds for catalytic applications. They must actually be considered as high performance products with functional properties, and not just chemical species.

Chapters devoted primarily to catalysis have been published in earlier volumes of the Handbook. In this volume several more are added. The first is an extension of the earlier chapter 43, on interactions at surfaces of metals and alloys, to reactions such as hydrogenation, methanation, ammonia synthesis, saturated hydrocarbon reactions, dehydrogenation of hydrogenated materials, hydrodesulfurization, and carbon monoxide oxidation. The second chapter reports on the wide variety of catalyzed reactions involving metals and alloys in the innovated form of metal overlayers or bimetallic compounds with some transition metals produced from ammonia solutions. This is followed by a chapter on catalysis with mixed oxides usually having perovskite or perovskite-related structures.

Then follows a comprehensive discussion on the background and current role of cerium oxide and associated materials for post-treatment of exhaust gases for pollution control. These three-way catalysts (TWC) are designed to render harmless the CO, NOx, and unburned hydrocarbons from internal combustion engines. The next chapter considers the wide field of zeolite catalysts containing rare earths from their historic use in petroleum refining in the 1960s to other petrochemical and fine chemical applications today. The final chapter documents the use of the triflates (the trifluoro-methane-sulfonyl group which is a hard Lewis acid in both aqueous and organic solutions) as versatile catalysts in carbon-carbon bond-forming reactions. Their stability in the presence of water, in spite of their being hard Lewis acids, enhances their growing usefulness.

Volume 15 in this series continues the voyage of discovery started almost a decade ago. Chapter 98 adds significantly to an evaluation of systematic, experimental low-temperature studies of the ambivalent behaviours of cerium (ferromagnetism, antiferromagnetism, spin glass, superconductivity etc.) which depend upon its environment in materials. The conclusions arrived at should provide new data against which the theory can be advanced. The next chapter provides a review of rare earth carbides, emphasizing the thermodynamics, phase diagrams, crystal structures and physical properties. The binary rare earth carbides present an exceptionally wide range of compositions and structures both as solids and gas-phase molecules. Complex carbides with additional metal and non-metal components also receive attention. Metal-rich halides (i.e. compounds with an X/R ratio <2) are the subject of the next chapter. The compounds are classified according to their structure and chemical bonding characteristics and their electrical and magnetic properties are also reviewed. Chapter 101 deals with the preparation, structure, chemical and physical properties of heavy-metal fluoride glasses. Large amounts of rare earths can be added into these, and they possess a great potential for optical applications in the mid-infrared range as fiber optic glasses for communication and transmission of information, optical wave guides, fiber lasers and sensors. The following chapter explores the chemical kinetics of solvent and ligand exchange in aqueous lanthanide solutions. A wealth of tabulated information on rate and equilibrium constants is provided in textual and tabular form. Chapter 103 considers the fundamentally important reactions of the lanthanide ions with water. These interactions are discussed for both solids and solutions. The hydrated species are considered in detail for the aqueous solution, revealing the consequences of the lanthanide series sequence. The concluding chapter reviews macrocyclic complexes formed by rare earth and dioxouranium ions as templates. Synthetic trends and reactivity are considered as well as potential uses of these intriguing wrap-around structures.

The rare earths play a unique role in science. These seventeen related elements afford a panoply of subtle variations deriving from the systematic development of their electronic configurations, allowing a test of theory with excellent resolution. In contrast they find widespread use in even the most mundane processes such as steel making, for polishing materials and gasoline cracking catalysts. In between are exotic uses such as TV screen phosphors, lasers, high strength permanent magnets and chemical probes. This multi-volume handbook covers the entire rare earth field in an integrated manner. Each chapter is a comprehensive up-to-date, critical review of a particular segment of the field. The work offers the researcher and graduate student alike, a complete and thorough coverage of this fascinating field.

This volume differs somewhat from the previous volumes in the series in that there is a strong emphasis on the physical aspects and not so much on the chemical aspects of intermetallic compounds. Two of the chapters are concerned with relatively new experimental methods of studying rare earth metallic phases - high energy neutron spectroscopy and light scattering. In these chapters the authors explain the new kinds of information one obtains from these techniques and how this complements the knowledge previously gleaned from the more common measurements - such as NMR, heat capacities, magnetic susceptibility, transport and elastic properties. One of the remaining three chapters deals with NMR studies of rare earth intermetallics and the final two chapters are concerned, not so much with a particular experimental technique, but with physical phenomena that occur in these compounds: the electron-phonon interaction and heavy fermion behavior.

This volume of the Handbook is the first of a two-volume set of reviews devoted to the rare-earth-based high-temperature oxide superconductors (commonly known as hiTC superconductors). The history of hiTC superconductors is a few months short of being 14 years old when Bednorz and Muller published their results which showed that (La, BA)2CuO4 had a superconducting transition of ~30 K, which was about 7K higher than any other known superconducting material. Within a year the upper temperature limit was raised to nearly 100K with the discovery of an ~90K superconducting transition in YBa2Cu3O7-&dgr;. The announcement of a superconductor with a transition temperature higher than the boiling point of liquid nitrogen set-off a frenzy of research on trying to find other oxide hiTC superconductors. Within a few months the maximum superconducting transition reached 110 K (Bi2Sr2Ca2Cu3010, and then 122K (TlBa2Ca3Cu4O11. It took several years to push TC up another 11 K to 133 K with the discovery of superconductivity in HgBa2Ca2Cu3O8, which is still the record holder today.

The contributions to this volume focus on selected chemical aspects of rare-earth materials. The topics covered range from a basic treatment of crystalline electric-field effects and chemical interactions in organic solvents, to separation processes, electrochemical beaviors which impact corrosion, oxidation resistance, chemical energy storage and sensor technology, and to analytical procedures.

Underlying the most subtle chemical and optical properties of these elements and their compounds in the condensed state are the crystal field effects. This phenomenon in non-metallic compounds is discussed in chapter six. The volume opens with a review of important new solvent extraction procedures as well as emerging alternative separation processes such as photochemical separation, precipitation stripping and supercritical extraction. Scientific and industrial procedures are illustrated. In a further chapter eight major analytical techniques of obtaining accurate trace analysis are examined, tabulated and assessed. The most effective procedures of each are also reviewed. Chapter two considers a wide variety of methods using rare-earth solutions and slats to modify advantageously the costly deterioration of metals and alloys. This topic is expanded in the following chapter, paying particular attention to protection against high-temperature oxidation, sulfidization and hot-salt corrosion. The following two chapters are concerned with the versatility of the rare earths in addressing current technical problems such the use of rare-earth intermetallics, principally LaNi3-based materials, to provide the skyrocketing need for environmetally friendly, usually portable, battery power. The final chapter is a review of the solvation, interaction and coordination of rare-earth salts in a variety of organic solvents including dimethylacetamide, dimethylsulfoxide, various alcohols, acetonitrile and propylenecarbonate under strict anhydrous conditions. A contrast of these interactions with those in which water is present with organic solvents is also made.

This volume of the handbook covers a variety of topics with three chapters dealing with a range of lanthanide magnetic materials, and three individual chapters concerning equiatomic ternary ytterbium intermetallic compounds, rare-earth polysulfides, and lanthanide organic complexes. Two the chapters also include information of the actinides and the comparative lanthanide/actinide behaviors.

Even at the beginning of the new millenium the rare earths still remain, to a certain extent, a mystery. The chapters in this volume will help to unravel some of these. In the filling of the 4f electronic orbitals the lanthanides defy the elementary aufbau principle that underlies the periodic sequence of the elements, and the authors of the first chapter introduce the readers to the basic physics of the orbital collapse leading to that failure. Furthermore an explanation is offered in terms of double-well potentials. The phenomenon is illustrated using the valence transitions observed in some of the rare earth atoms, including Sm group metals and the higher oxides of cerium, praseodymium and terbium. In the second chapter the synthesis and structure of the many types of rare earth halides are described. They have been described as simple, complex, binary, ternary and multinuclear complex, and other categories needed to deal with the most studied of the rare earth compounds. The structure types are skillfully illustrated to show the elementary architecture of each type.
In chapter three the authors discuss the science and applications of rare earth super ionic conductors as solid electrolytes. Conduction by oxygen and fluorine anions as well as hydrogen and other cations associated with these electrolytes is emphasized. They deal with extrinsic and intrinsic types together with their associated structures and structural types including structural defects. The chapter concludes with an outline of the many applications of solid electrolytes.
Chapter four introduces the reader to the principles that underlie thermoluminescence and its application to dosimetry and provides detailed information on the R-activated phosphors that support dosimetry. This is a selective review of detailed literature based on the areas making most progress.
The final chapter elaborates on the data gained by the studies and interpretation around the analytical separation of the individual rare earth elements utilizing chromatographic techniques. The authors describe the fundamental chemistry that underpins contemporary analytical separation techniques for lanthanide separation and analysis. This is done after a description of the rich assortment of separation methods in use has been introduced.

The simple words of love from a gentle heart. Selected works of poetry