Structural, Electronic, and Physical Properties of Solid-State Rare-Earth Boride Carbides
Abstract
Ternary rare-earth and actinoid metal boride carbides RxByCz (R = Sc, Y, Ln, Ac) have been intensively investigated for a number of decades with respect to their extremely broad crystal chemistry and their greatly varying physical properties. In contrast to many intermetallic compounds, the B ↔ C substitution in the rare-earth metal boride carbides is not easy to evidence. This chapter takes a deeper look at the crystallography, electronic structures, and properties of the rare-earth and actinoid metal boride carbides. Crystal structures of the RxByCz phases display a variety of different arrangements with boron–carbon substructures ranging from zero-dimensional units to one-dimensional chains and two-dimensional networks embedded in the metal atom sublattices. Rare-earth metal boride carbides exhibit relatively complicated structure types, which are not observed among carbides or borides, nor among silicides, germanides, aluminides, or gallides. Up to now, more than 140 rare-earth metal and actinoid metal boride carbides have been reported. They crystallize with 38 different structure types. Phase diagrams, structural and physical data on ternary systems, and compounds containing rare earth, actinoid, boron, and carbon known through the beginning of 2018 and methods of their synthesis are critically reviewed. These data can be used for the prediction and synthesis of new ternary boride carbides for basic research as well as for applications. © 2018 Elsevier B.V.