The effect of sintering atmospheres on the properties of CSBT-0.15 ferroelectric ceramics

Ca0.15Sr1.85Bi4Ti5O18 (CSBT-0.15) ferroelectric ceramics were developed by the conventional solid-state reaction method under various sintering atmospheres. The influences of these sintering atmospheres on grain orientation, grain size, oxygen vacancies, ferroelectric properties and leakage mechanisms were systematically investigated. It was found that the samples sintered under N2 showed higher a-axis orientation and smaller grain sizes than those sintered under O2 and air. From XPS analysis, it can be observed that the amount of Ti3+ in the ceramics sintered under N2 is relatively high, which indicates a high number of oxygen vacancies in these samples. The samples sintered under N2, air and O2 all delivered well-saturated hysteresis loops with a remnant polarization (2Pr) of 13.8 μC/cm2, 12.4 μC/cm2 and 7.2 μC/cm2 and corresponding coercive fields (2Ec) of 100 kV/cm, 86 kV/cm and 80 kV/cm, respectively. At 70 kV/cm, the leakage current densities of the samples sintered under N2, air and O2 are 4.2 × 10−6 A/cm2, 1.9 × 10−6 A/cm2 and 1.0 × 10−6 A/cm2, respectively. The leakage conduction mechanism transformed from Ohmic conduction in a relatively low applied electric field range (0-15 kV/cm) to space-charge-limited conduction (SCLC) in higher electric field ranges.