SynopsisIn keeping with the tradition of the Handbook, volume 35 covers a wide diversity of topics involving the rare earth elements. The topics range from solid oxides for advanced, energy efficient electrical power generation (Chapter 223); to the oxo-selenate members of the vast family of complex oxo-anions; to organic beta-diketonate complexes (Chapter 225); to the utilization of organic complexes for molecular recognition and sensing (Chapter 226).Natsuko Sakai, Katsuhiko Yamaji, Teruhisa Horita, Yue Ping Xiong and Harumi Yokokawa examine the role of yttria stabilized zirconia, R2O3-ceria, rare earth-alkaline earth manganites, and rare earth cobaltites, chromates and titanates as solid oxide fuel cell (SOFC) components, i.e. the electrolyte, anode, cathode and interconnects.Mathias Wickleder's review focuses on one particular family of oxo-compounds, which has been studied extensively in the past few years because of their rich structural chemistry, complex thermal behaviors and dual oxidation states {selenites [or oxo-selenate (IV)] and selenates [or oxo-selenate (VI)]}.Koen Binnemans points out that the rare earth b-diketonates, which have been known for about 100 years, are one of the most extensively investigated rare earth coordination compounds. This popularity is due to the fact that they are easily synthesized, readily available from commercial sources, and have many applications.Satoshi Shinoda, Hiroyuki Miyake, and Hiroshi Tsukube have summarized the recent advances in the chemistry of rare earth complexes in molecular recognition and sensing technology. When a lanthanide containing receptor binds with a given substrate, specificinteractions may occur in the inner and/or outer coordination sphere(s), and by monitoring these resultant interactions precise information can be obtained about compounds (i.e. amino acids, proteins) and living organs.