The structure of yttrium cobaltate from neutron diffraction

The crystal structure of YCoO3 has been determined from Rietveld analysis of the powder neutron diffraction data at 17, 100, and 300 K. At each temperature, the structure is a distorted perovskite with orthorhombic symmetry, space group Pbnm (Z = 4). The lattice parameters, at 300 K, are 5.1388(5) x 5.4191(5) x 7.3658(7) Angstrom. Structural analysis indicates that the formal valence of cobalt in YCoO3 is +3. Analysis of the Co-O distances and the absence of magnetic structure indicates 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 Co3+ ions at 300 K (but insignificant fractions at 100 and 17 K) are in the high-spin state. (C) 1997 Academic Press.