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

摘要

A modified and convenient route using microemulsions (avoiding Ba-alkoxide) was evolved for the synthesis of uniform and monodisperse nanoparticles of BaTiO_3 at low temperature (800 deg 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 deg C to 120 nm at 1100 deg 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 deg C sintering) to 520 (1100 deg C sintering) at 100 kHz. The dielectric constant was highly stable with temperature as well as frequency.