Synthesis And Characterization Of BaTiO₃, Ferrites And Their Nanocomposites

In recent years, much attention has been given to nanometer powders. Theirphysical and chemical properties are dependent on particle size, which might bedifferent from that of bulk materials. BaTiO₃ and ferrites nanometer powders areindispensable in electron industry. Synthesis and characterization of BaTiO₃ andferrites nanoparticles as well as their respective nanocomposites have attractedconsiderable attentions.Among many techniques used to fabricate nanometer metal powders, thewire electrical explosion method is a promising one. In this paper, the Ninanoparticles are synthesized by WEE under Ar condition. Ni nanoparticles areinvestigated by X-ray diffraction technology to study their structure and latticecontraction. The average particle size of as-prepared nanoparticles is studied bythe software package of line shape analysis with the method of Fourier analysis,and the average particle size is 52 nm. TEM and FESEM photos show that Ninanoparticles are spheres with uniform particle size distribution.BaTiO₃ nanoparticles with cubic perovskite structure have been prepared at60 ℃ through coprecipitated method. But there are a few BaCO3 as impurity.We synthesize Ni-BaTiO₃ nanocomposites with the same method. The structure,morphology image and magnetization of as-prepared nanocomposites areinvestigated by X-ray diffraction technology, TEM, FESEM and VSM. Thenanocomposites consist of Ni, BaTiO₃ and BaCO₃. The particles are nearlyspheres, and there is clear core-shell structure in TEM photo. From thecomparison of magnetization between Ni and Ni-BaTiO₃, it can be seen that thesaturation magnetization of Ni-BaTiO₃ nanocomposites is lower than that of Ninanopowders but the coercivity of Ni-BaTiO₃ nanocomposites is almost the sameas that of Ni nanopowders. This phenomenon can be attributed to the content ofNi in unit mass Ni-BaTiO₃ nanocomposites is lower than that of pure Ni.SrFe12O19 and CoFe2O4 nanoparticles are respectively prepared by usingcoprecipitate technique, and SrFe12O19-CoFe2O4 nanocomposites are alsoprepared by the same technique. With the coprecipitate technique, we can obtainSrFe12O19 nanoparticles which contain a few Fe2O3 and we can get pure cubicspinel type CoFe2O4 nanoparticles. TEM photos reveal the formation of CoFe2O4shell on SrFe12O19 nanoparticles. The microwave absorption behavior of theSrFe12O19 nanopowders and SrFe12O19-CoFe2O4 nanocomposites is different.The specimen of SrFe12O19-CoFe2O4 nanocomposites shows lower reflectionratio and wider bandwidth. The microwave absorption behavior ofSrFe12O19-CoFe2O4 nanocomposites with different content indicates that thecontent of microwave absorber can significantly affect the microwave propertiesof absorber. The absorption ratio increases from 0.2 db to 2.6 db as the content ofabsorber decrease from 70 % to 30 %.Cobalt ferrite nanoparticles have been synthesized by using coprecipitatetechnique at different temperatures. The effect of reaction temperature on theparticle size and magnetic properties of the nanoparticles have been studied.XRD patterns, TEM and FESEM micrographs show the formation of equiaxialshaped single-phase cubic spinel structure and the increase of particle size withthe increasing reaction temperature. Raman spectra confirm the formation ofCoFe2O4 nanoparticles. The results of VSM indicate that the saturationmagnetization of CoFe2O4 increases with the increase of reaction temperatureand shows a maximum saturation magnetization of 29.5 emu/g at roomtemperature. The variations of coercivity and remanence ratio are dependent onthe particle size. The maximum values of coercivity and remanence ratio are3267 Oe and 0.58, respectively. The variations may be attributed to the singledomain size of ca. 34 nm, below and above which the magnetization mechanismfor particles will be different. The critical size of superparamagnetictransformation is about 9 nm determined by TEM and FESEM.