Preface

The first chapter (236) in this volume of the Handbook on the Physics and Chemistry of Rare Earth is a recapitulation of the scientific achievements and contributions made by the late Professor LeRoy Eyring (1919–2005) to the science of the lanthanide oxides in which the lanthanide element has a valence equal to or greater than three. Although LeRoy had a broad range of interests in the chemistry of the rare earths and actinides the main focus of his outstanding scientific career was concerned with the lanthanide higher oxides. This chapter was written by Dr. Zhenchuan Kang his last post doctoral associate. Professor Eyring was a co-editor of the first 32 volumes of the Handbook. The remaining four chapters of volume 38 describe rare earth compounds which have three or more chemical constituents. Chapters 237 through 239 deal with metallic-like systems/compounds, while the last one (240) is concerned with discrete anionic assemblies intermediate in size between a molecule and a bulk solid—the polyoxometalates. Chapter 237, which reviews the rare earth–transition metal–plumbides, is a continuation of reviews on ternary rare earth–transition metal–nontransition elements (such as silicon, germanium, tin and indium) systems and covers phase relationships, crystallography and physical properties. The higher borides, i.e. compounds with boron contents greater than 6 for every metal atom, both binary and ternary systems are examined in chapter 238. The boron atoms form cages in which the rare earth metals reside and a number of unusual phenomena have been discovered in these covalently bonded atomic networks. The magnetic and superconducting behaviors of the quaternary rare earth–nickel– boron–carbon compounds, RNi2B2C, is the main topic covered in chapter 239, with the emphasis being the interplay between co-existing magnetism and superconductivity. The last, chapter 240, covers the structures, photophysical properties, catalytic behaviors and biological applications of the complex rare earth compounds formed with hexavalent molybdenumor tungsten-containing metalate anions.