Influences of protective atmosphere on the characterization and properties of NaSr2Nb5O15 lead-free piezoelectric ceramics by sol–gel method

NaSr2Nb5O15 lead-free piezoelectric ceramics were prepared by the sol–gel method, they were sintered at different temperatures with or without protective atmosphere. The influences of sintering temperature and protective atmosphere on the characterization and properties of the ceramics were investigated. All the ceramics showed the pure tungsten bronze structure and an intermediate relaxor-like behaviour between normal and ideal relaxor ferroelectrics according to the modified Curie–Weiss law. The sintering temperature affected significantly the properties of ceramics, with the sintering temperature increased both with and without protective atmosphere, the e r, d 33, K p and P r of these ceramics initially increased and decreased finally, whereas the variation of Q m and E c showed the opposite tendency. Furthermore, the protective atmosphere also significantly affected the properties of these ceramics, e r, d 33, K p and P r of such ceramics sintered with protective atmosphere were superior to those of the ceramics sintered without protective atmosphere, while the tan δ, Q m and E c gave the contrary results.