Publication date: 1 February 2018
Source:Journal of Crystal Growth, Volume 483
Author(s): Martin Breitenbach, Stefan G. Ebbinghaus
Composites consisting of ferrimagnetic CoFe2 O4 and ferroelectric Ba1−x Srx TiO3 were grown by the floating zone technique. The influence of Sr substitution, growth rate and atmosphere during the floating zone process were investigated. The formation of the non-ferroelectric, hexagonal modification of BaTiO3 was avoided by a slight Sr substitution of 3 mol% and the formation of BaFe12 O19 was suppressed using pure nitrogen as atmosphere during the floating zone melting. These synthesis parameters led to phase-pure, but electrically conductive CoFe2 O4 -Ba1−x Srx TiO3 composites. A thermal treatment at 973 K in air resulted in a strong increase of the electric resistivity accompanied by a decrease of the unit-cell parameters of both components indicating the healing of oxygen defects. SEM investigations revealed a variety of different geometric structures and crack-free interfaces between both phases. The low porosities observed in the micrographs correspond with densities above 90%. Magnetoelectric (ME) measurements confirmed a coupling between the ferroic orders of both phases with a hysteresis and maximum αME of 1.3 mV Oe−1 cm−1.
Source:Journal of Crystal Growth, Volume 483
Author(s): Martin Breitenbach, Stefan G. Ebbinghaus