THE SOLID-SOLUTION BAFE12-2XCOXTIXO19 O-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-6) - CATIONIC DISTRIBUTION BY NEUTRON-DIFFRACTION

The solid solution BaFe12-2xCoxTixO19 has been prepared in the range 0 less-than-or-equal-to x less-than-or-equal-to 6. The crystal structur e and cationic distribution between the different metallic sublattices of the magnetoplumbite structure have been refined from high resoluti on neutron powder diffraction data. Our results show that the preferen ce of Fe3+, Co2+, and Ti4+ for the different sublattices can be modele d considering three regions in the whole compositional range. In this system, Co2+ has a preference for tetrahedral positions, probably due to the fact that Ti4+ has a stronger preference for octahedral positio ns. This fact explains why the end member of the series, BaCo6Ti6O19, can be easily prepared. The hypotheses for the cationic distribution a re validated by the reasonable agreement obtained from comparison of t he average observed metal-oxygen distances with the expected distances from the valence bond approach for each site. (C) 1994 Academic Press , Inc.