Syntheses of Rare Earth Dioxymonocyanamides (Ln2O2CN2, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd)

A series of new compounds were prepared by heating Ln2O3 (Ln = La, Nd, Sm, Eu, Gd), Pr6O11, or Ce2(CO3)3·8H2O in the presence of carbon under an ammonia atmosphere. Thermogravimetric and CHN analyses revealed that these compounds are of rare earth dioxymonocyanamides (Ln2O2CN2). They are classified into two structure types depending on Ln3+ ionic radii, viz., type I (tetragonal) for Ln = La, Ce and type II (trigonal) for Ln = Ce, Pr, Nd, Sm, Eu, Gd. Ce2O2CN2 takes both structure types depending upon preparative temperature.