Nanostructured barium titanate prepared through a modified reverse micellar route: Structural distortion and dielectric properties

A modified and convenient route using microemulsions (avoiding Ba-alkoxide) was evolved for the synthesis of uniform and monodisperse nanoparticles of BaTiO3 at low temperature (800 degrees C). X-ray line broadening and transmission electron microscopy studies show that the particle size varies in the range of 20-25 nm. Evidence for tetragonal distortion was found in these nano-sized (20-25 nm) particles of barium titanate from careful x-ray diffraction studies as well as from Raman spectroscopy. Our study showed that the critical size of the cubic to tetragonal transition in barium titanate may be much lower than suggested theoretically. The grain size showed an increase on sintering of 35 nm at 900 degrees C to 120 nm at 1100 degrees C, which was much lower than the grain size obtained at this temperature by the normal solid state route. The dielectric constant depends on sintering temperature and was found to increase from 210 (900 degrees C sintering) to 520 (1100 degrees C sintering) at 100 kHz. The dielectric constant was highly stable with temperature as well as frequency.