THE CRYSTAL-STRUCTURE OF A NEW QUATERNARY FERRITE - BA12FE28TI15O84

The quaternary ferrite Ba12Fe28Ti15O84 has monoclinic symmetry, space group C2 m, a = 9.988(7), b = 17.298(9), c = 19.17(2) Å, β = 99.33(6)°, Z = 2. The crystal structure was refined to Rw = 0.048 for 2283 independent reflections collected on a Philips PW1100 diffractometer using AgKα radiation. The structure is based on a close packed array of Ba + O atoms with a 24-layer stacking sequence (cchcccch)3 along c* and with metal atoms occupying both octahedral and tetrahedral interstices. The iron and titanium atoms are substantially ordered into blocks of cubic stacked layers centered at z = 0 and 1 2, respectively. The titanium rich segments have a structure closely related to cubic BaTiO3 while the iron rich blocks have features in common with the spinel structure. The two blocks are joined via a transition layer containing both titanium- and iron-rich octahedra. © 1991.