A comparative study of dielectric and ferroelectric properties of sol–gel-derived BaTiO₃ bulk ceramics with fine and coarse grains

Abstract

Fine and coarse-grained BaTiO₃ (BTO) ceramics were prepared by conventional sintering of sol–gel-derived BTO nanopowders at 1150 and 1350 °C, respectively. Based on characterization results, fine and coarse-grained BTO ceramics had an average grain size of about 1 and 12 µm, respectively. They exhibited a tetragonal structure with tetragonality (c/a ratio) of 1.0105. The dielectric properties of fine and coarse-grained BTO ceramics were measured in the frequency range of 100 Hz–10 MHz and temperature range of −45–180 °C. A dominant dielectric relaxation was observed at high frequency above 1 MHz for both BTO ceramics. Room-temperature dielectric constant of fine-grained BTO (1502) was greater than that of coarse-grained BTO (1082) at 1 kHz due to the grain size effect. For temperature dependence measurement, dielectric constant of fine-grained BTO was less sensitive with changing temperature at phase transition than coarse-grained BTO. Polarization–electric field (P–E) loop of coarse-grained BTO at room temperature revealed a well-defined hysteresis loop, confirming its ferroelectric switching behavior. In contrast, a lossy hysteresis loop was found for fine-grained BTO owing to its high leakage current. Our results in this work provide a useful information and progress in the dielectric and ferroelectric properties of sol–gel-derived BTO bulk ceramics.