Effects of A-Site (NaCe) Substitution with Na-Deficiency on Structures and Properties of CaBi4Ti4O15-Based High-Curie-Temperature Ceramics

Three kinds of bismuth-layer-structured ferroelectric (BLSF) ceramics, CaBi4Ti4O15 (CBT), Ca0.8(CeNa)0.1Bi4Ti4O15 (CNBT), and Na-deficient Ca0.8(Ce0.1Na0.050.05)Bi4Ti4O15 [CN] (where represents vacancies) were prepared by a conventional ceramic technique. X-ray powder diffraction showed that their crystal structures are a single phase of BLSF with m=4. Sintering characteristics of the three ceramics were also discussed. Scanning electron microscope (SEM) micrographs of CN showed that the grain is platelike. The A-site (NaCe) substitution can improve the piezoelectric constant d 33 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 very high piezoelectric constant d 33 and high-temperature resistivity but also increases the Curie temperature. The reason for the high T c (T c=866°C) of CN is considered to be internal stress. As a result, Na-deficient CN ceramic is found to be an excellent high-temperature piezoelectric material.