Structure and electrical properties of bismuth and sodium modified SrBi₂Nb₂O₉ ferroelectric ceramics

Sr_1-x(Bi, Na)_x/2Bi₂Nb ₂O₉ (SBNBNO, x = 0, 0.2, 0.4 and 0.6) ceramics were prepared by the conventional solid-state route. X-ray diffraction analyses (XRD) and Raman spectroscopy indicated that all specimens have a single phase with perovskite-type orthorhombic structure. The piezoelectric activity and Curie temperature of SrBi₂Nb₂O₉ (SBN) ferroelectric ceramics are significantly improved by bismuth and sodium modification. The piezoelectric coefficient d₃₃ of the Sr_0.6(Bi, Na) _0.2Nb₂O₉ (SBNBN4) specimen was found to be 22 pC/N, which is higher than the d₃₃ values (about 12 pC/N) of SBN specimen. Moreover, the SBNBN4 specimen exhibited the excellent temperature stability of piezoelectric properties. In order to confirm the nature of the piezoelectric properties enhanced, the relationship between the structure and electrical properties was discussed.