Synthesis And Characterization Of Peroviskite Structure And Multiferroic Materials Via EDTA-citrate Gel Process

The nanopowders, including SrTiO3 ,PbTiO3 and Bi2O3 ·3TiO2 weresynthesized via a citric-EDTA gel process for high-voltage capacitor applications.The decomposition processes of the precursors were investigated by thermalanalysis (DTA/TG/DTG) and X-ray diffraction (XRD). The sintered ceramicsamples derived from so-prepared powders were observed by Scan electronicmicroscopy (SEM), and the dielectric properties of the ceramic samples weremeasured. The results indicate that the nanopowders exhibit good sinterability,and the resulting ceramics have fine grain size and good dielectric properties. Magnetoelectric CoFe2O4-BaTiO3 nanopowders were synthesized by threedifferent ways, including mixing CoFe2O4 powders with BaTiO3 powders,coating BaTiO3 shells on CoFe2O4 cores via a sol-gel process and synthesizingCoFe2O4-BaTiO3 composites by a modified Pechini method. The measurementwas carried out to investigate the electric and magnetic properties of the bulkcomposite materials derived from these powders. The experimental resultsshowed that so-prepared bulk materials contained both ferroelectric andferromagnetic phases,consequently ferroelectricity and ferromagnetism beingobserved. BaTiO3 phase in the composites obtained from the modified Pechinimethod was of the largest lattice constant ratio (c/a), comparing with that in thecomposites made by the other methods. Furthermore, this composite material hadoutstanding dielectric, piezoelectric and magnetoelectric properties. Particularlythe maximum magnetoelectric voltage coefficient of this composite materialreached 2.54V/cm*oe under the optimal magnetic bias of 0.27Koe, which was 13times higher than the best reported in literature. The EDTA – citrate gel process was used to prepare microwave dielectricBaTi4O9 ceramics. The morphology and the dielectric properties of the resultingBaTi4O9 ceramics, fully densified at 1150oC for 2 hours, were also investigated.