Synthesis and electrical properties of sodium bismuth niobate Na0.5Bi2.5Nb2O9

The crystal structure of Na0.5Bi2.5Nb2O9 was refined from its powder X-ray diffraction (XRD) data. Sodium bismuth niobate at 23 °C is orthorhombic, A21am, with a=5.4998(3) Å, b=5.4602(2) Å, c=24.952(1) Å, and Z=4. The piezoelectric properties were investigated using the dense bulk ceramics. The electromechanical coupling coefficients (kij) and electrical quality factors (Qm) are k31=3.2%, kt=10.0%, and Qm=3800. Single crystals were also grown from stoichiometric melts using a slow cooling technique. The dielectric and ferroelectric properties of the crystal indicates that a spontaneous polarization clearly occurs in the crystallographic a–b plane.