THE STRUCTURE OF YTTRIUM COBALTATE FROM NEUTRON-DIFFRACTION

The crystal structure of YCoO3 has been determined from Rietveld analy sis of the powder neutron diffraction data at 17, 100, and 300 K. At e ach temperature, the structure is a distorted perovskite with orthorho mbic symmetry, space group Pbnm (Z = 4). The lattice parameters, at 30 0 K, are 5.1388(5) x 5.4191(5) x 7.3658(7) Angstrom. Structural analys is indicates that the formal valence of cobalt in YCoO3 is +3. Analysi s of the Co-O distances and the absence of magnetic structure indicate s that the majority of the Co3+ ions in YCoO3 are in the low-spin (i.e . t(2g)(6)l(g)(0)) state. The data also show that perhaps 10% of the C o3+ ions at 300 K (but insignificant fractions at 100 and 17 K) are in the high-spin state. (C) 1997 Academic Press.