Fine-grained BaTiO3–MgFe2O4 composites prepared by a Pechini-like process

Abstract

The synthesis of BaTiO3–MgFe2O4 composite powders by a Pechini-like one-pot process and resulting ceramic bodies is described herein. Phase formation during the decomposition of homogenous (Ba, Ti, Fe, Mg)-gels was monitored up to 1200°C. Composite powders consisting of BaTiO3 and MgFe2O4 were obtained after decomposition at 700°C for 1h resulting in crystallite sizes of about 10nm. The shrinkage and sintering behaviour of compacted powders were examined. Sintering at ⩾1200°C leads to the formation of hexagonal BaTiO3 only for composites with a MgFe2O4 content of ⩾30wt.%. SEM images of ceramic bodies reveal that the MgFe2O4 particles are surrounded by BaTiO3 crystallites. Magnetic measurements of both powders and corresponding ceramic bodies show ferrimagnetic behaviour with low coercivities. At high-field and low temperatures an additional small paramagnetic contribution was observed which increases with decreasing MgFe2O4 content and should be considered by the calculation of the saturation magnetization.Finally, the frequency dependent variation of the relative permittivities of the composites was investigated.