SYNTHESIS AND CHARACTERISATION OF NEW QUATERNARY BOROCARBIDES RRH2B2C (R = RARE EARTH)

摘要

Arc-melting syntheses of RRh2B2C were carried out for all lanthanide elements except promethium. X ray diffraction revealed that new compounds exist for R = Y, La-Er (except Eu), and the stability of RRh2B2C decreases for the smaller lanthanide, The tetragonal a-axis of RRh2B2C was found to contract as R goes from La to Er. The c-axis, however, expands slightly, In accordance with the lattice parameter change, interatomic distances between Rh atoms decrease significantly from 2.7623 Angstrom in LaRh2B2C to 2.6552 Angstrom in ErRh2B2C. The reduced stability of the RRh2B2C phase for the smaller rare earth is explained by the change in the crystallographic parameters with the size of R. (C) 1997 Academic Press. [References: 18]