EFFECTS OF A-SITE (NaCe) SUBSTITUTION WITH Na-DEFICIENCY ON STRUCTURES AND PROPERTIES OF CaBi4Ti4O15-BASED HIGH-CURIE-TEMPERATURE CERAMICS

Three kinds of Bi-layer-structured ferroelectric (BLSF) ceramics, CaBi4Ti4O15 (CBT), Ca0.8(CeNa)0.1Bi4Ti4O15 (CNBT), and Na-deficient Ca0.8(Ce0.1Na0.05\Box0.05)Bi4Ti4O15 [CN\BoxBT] (where \Box represents vacancies) were prepared by a conventional ceramic technique. Powder XRD showed that their crystal structures are a single phase of BLSF with m=4. Sintering characteristics of the three ceramics were also discussed. SEM micrographs of CN\BoxBT showed that the grain is platelike. The A-site (NaCe) substitution can improve the piezoelectric constant d33 and high-temperature resistivity with decreasing Curie temperature. The modification by A-site (NaCe) substitution with Na-deficiency is more pronounced than CNBT, which not only leads to a high piezoelectric constant d33 and high-temperature resistivity but also increases the Curie temperature. The reason for the high Tc (Tc=866 C) of CN\BoxBT is internal stress. As a result, Na-deficient CN\BoxBT ceramic is an excellent high-temperature piezoelectric material. 16 refs.