Nanocrystalline non-stoichiometric SBT: Effect of milling duration on structural and electrical characteristics

In the present work, nanocrystalline specimens of non-stoichiometric Strontium Bismuth Tantalate (SBT) ferroelectric ceramics were synthesized by mechanical activation process using a high energy planetary ball mill. The powders were milled for different milling durations (5, 10, 20 h) keeping the milling speed fixed at 300 rpm. Microstructural characterizations have been performed using X-ray diffraction, scanning electron microscopy, electron diffraction and transmission electron microscopy. Nanocrystallites with average grain size in the range of 30–50 nm are observed to be formed. Grain size is observed to decrease with increasing milling duration. Detailed dielectric study as a function of temperature has been carried out. It is observed that dielectric constant increases and dielectric loss decreases with increasing milling duration. The observed characteristics have been explained in terms of increased number of grain boundaries due to the reduction of granular size.