Dielectric and piezoelectric properties of Na0.5Bi4.5Ti4O15―(x―1)Na0.5Bi0.5TiO3 composite ceramics

Na0.5Bi4.5Ti4O15-(x - 1)Na0.5Bi0.5TiO3 (2 < = x < = 99) ceramics have been prepared via the conventional ceramic technique. Over the wide composition range of 2 < = x < = 99, the coexistence of a bismuth layer-structured Na0.5Bi4.5Ti4O15 phase and a perovskite Na0.5Bi0.5TiO3 phase has been determined in these ceramics using dielectric and XRD techniques. It is found, interestingly, that near-zero temperature coefficients of the dielectric constants can be achieved in the 2 < x < 4 composite ceramics in the high-temperature region of 350-500 deg C. Since the x = 2-4 samples still have a considerable piezoelectric constant d33 that is higher than 11 pC/N after annealing at 600 deg C, these composite ceramics are thought to be a new kind of potential piezoelectric material for high-temperature applications.