TRANSFORMATION STUDIES OF M-TYPE TO W-TYPE HEXAFERRITE IN BAFE12-2XCO3XO19

Samples of general formula BaFe12-2xCo3xO19 (x=0.1, 0.3, 0.5) have bee n synthesized by ceramic as well as citrate gel routes. The X-ray diff raction patterns indicate that M-type phase forms for x=0.1, while W-t ype phase is favourable for x=0.3 and 0.5. The results tor x=0.3 are p articularly interesting. While the X-ray diffraction data show evidenc e of a monophasic W-type hexaferrite, the magnetic, thermal and micros tructural investigations indicate a secondary phase presumably at grai n boundaries. Transformation of M- to W-type hexaferrite has been expl ained in terms of different possibilities such as nucleation of second ary phases, formation of vacancies and different site occupation of io ns in the structure.