CRYSTAL-STRUCTURE OF THE OXIDENITRIDE, LI16NB2N8O

Crystals of rhombohedral Li16Nb2N8O (space group <R(3)over bar (h)>, N o. 148, Z=3, a=5.984(4) Angstrom, c=25.484(8) Angstrom) were obtained during a study of the Li-Ba-Nb-N system when a mixture of Li, Ba, and Nb confined in quartz was heated at 850 degrees C under flowing N-2. R efinement of single crystal data based upon F-2 yielded R2=0.024 and w R2=0.047. Li16Nb2N8O crystallizes isotypically with Li16Ta2N8O in an a nti-fluorite type superstructure. The Nb and two of the four independe nt Li ions are tetrahedrally coordinated by nitrogen anions; the remai ning two Li ions are tetrahedrally coordinated by one oxygen and three nitrogen anions. The compound can also be prepared by heating a Li3N: Nb2O5:NbN=16/3:1/5:8/5 molar mixture under flowing Ar/N-2 at 900 degre es C for 24 h. Magnetic susceptibility data between 10 and 300 K exhib it temperature independent paramagnetism. (C) 1996 Academic Press, Inc .