CRYSTAL-STRUCTURE AND CHARGE COMPENSATION MECHANISMS IN A BARIUM POTASSIUM BETA-FERRITE

The structure of a mixed-ion Ba2+-K+ beta-ferrite, Ba0.39K0.39Fe11O17. 03, has been determined by X-ray diffraction, and refined in the hexag onal space-group P6(3)/mmc, R(F)=3.4%, R(W)(F-2)=5.9%. At least two po ssible charge compensation mechanisms could be identified: (i) a Frenk el defect of Fe3+ ions indicating an extra oxygen ion in the conductio n plane, and (ii) Fe2+ ions and/or vacancies at Fe3+ ion sites in the spinel block. The K+ ions and most of the Ba2+ ions in the conduction plane are found at a 6(h) site near the 2(d) (Beevers-Ross) site; the remainder of the Ba2+ ions are at a 6(h) site at x approximate to 0.88 , y=-x.