Reverse micellar route to nanocrystalline titanates (SrTiO3, Sr2TiO4, and PbTiO3):: Structural aspects and dielectric properties

Nanoparticles of strontium titanates (SrTiO3, Sr2TiO4) and lead titanate (PbTiO3) have been obtained using reverse micelles as nanoreactors. Powder X-ray diffraction studies of the powders after calcining at 800 degrees C show monophasic SrTiO3, Sr2TiO4, and PbTiO3. X-ray line broadening studies and transmission electron microscopic studies show spherical grains of 30-40 nm size for strontium titanates, while PbTiO3 is obtained in the form of nanorods. The dielectric constant of SrTiO3 and Sr2TiO4 is found to be 90 and 30, respectively, (at 100 kHz) for samples sintered at 1000 degrees C. PbTiO3 shows a dielectric constant of 160 (at 100 kHz) after sintering at 900 degrees C. The dielectric constant of Sr2TiO4 (with temperature) is highly stable. The temperature variation studies of the dielectric constant of PbTiO3 show a ferroelectric phase transition at 490 degrees C (1 kHz). The T-c varies with frequency and is found to decrease to 470 degrees C at 100 kHz.