Effects of A-site (NaCe) substitution with Na-deficiency on structures andproperties of CaBi4Ti4O15-based high- Curie-temperature ceramics

Three kinds of bismuth-layer-structured ferroelectric (BLSF) ceramics, CaBi 4Ti4O15 (CBT), Ca-0.8(CeNa)(0.1)Bi4Ti4O15 (CNBT), and Na-deficient Ca-0.8(C e(0.1)Na(0.05)square (0.05))Bi4Ti4O15 [CN square BT] (where square represen ts vacancies) were prepared by a conventional ceramic technique. X-ray powd er diffraction showed that their crystal structures are a single phase of B LSF with m = 4. Sintering characteristics of the three ceramics were also d iscussed. Scanning electron microscope (SEM) micrographs of CN square BT sh owed that the grain is platelike. The A-site (NaCe) substitution can improv e the piezoelectric constant d(33) and high-temperature resistivity with de creasing Curie temperature. The modification by A-site (NaCe) substitution with Na-deficiency is more pronounced than CNBT, which not only leads to a very high piezoelectric constant d33 and high-temperature resistivity but a lso increases the Curie temperature. The reason for the high T-c (T-c = 866 degreesC) of CN square BT is considered to be internal stress. As a result , Na-deficient CN square BT ceramic is found to be an excellent high-temper ature piezoelectric material.