Controllable defects and electrical properties of nonstoichiometric Na0.5-xBi0.5+xBi2Nb2O9 high temperature piezoceramics

High temperature piezoelectric materials have attracted much attention owing to their potential applications for structural health monitoring and nondestructive evaluation in new jet engines, steam and nuclear plants. Nonstoichiometric (Na0.5-xBi0.5+x)Bi2Nb2O9 high temperature piezoceramics were prepared by a conventional solid-state sintering route. The microstructure, dielectric, DC resistivity and piezoelectric properties were investigated. Pure Aurivillius phase structure only existed in a narrow region (−0.02 ≤ x < 0.02). Moreover, the anisotropic grain morphologies were significantly restrained by increasing Bi contents. The oxygen vacancies were artificially tailored in nonstoichiometric compositions. The dynamic piezoelectricity as a function of the poling electric field was also studied and underlying physic mechanism was discussed. (Na0.48Bi0.52)Bi2Nb2O9 ceramic has the large piezoelectric coefficient (d33∼20.8pC/N), high Curie-temperature (TC∼796 °C) and low thermal aging rate (<10% @700 °C), indicating that it is a promising candidate for ultra-high temperature piezoelectric sensor applications.