Structural, electrical and electromechanical properties of [(Bi0.5Na0.5)0.935Ba0.065)]1-yLay (Ti1-zTaz)O3 lead-free piezoelectric ceramics

Piezoceramic systems [(Bi0.5Na0.5)(0.935)Ba-0.065)](1-y)LayTi1-zTazO3 (BNBT-LT) with (y, z) = (0, 0), (0.01, 0.01), (0.02, 0.01), (0.03, 0.01) and (0.04, 0.01) have been synthesized using solid state reaction method. The effect of La3+ and Ta5+ on the structural, ferroelectric, dielectric, bipolar and unipolar strain properties of the parent matrix BNBT was studied. X-ray diffraction (XRD) spectra of samples with (y, z) <= (0.01, 0.01) were of ABO(3) character and indexed according to the coexistence of rhombohedral and tetragonal symmetry; whereas the systems with (y, z) = (0.02, 0.01), (0.03, 0.01) demonstrated coalescence of reflections (200) & (002) into a single peak (200), indicating a (rhombohedral & tetragonal) <-> (pseudocubic) structural phase transition. The polarization & strain vs. field loops of the LT rich systems displayed diffused phase transition. The system (x, y) = (0.02, 0.01) attained highest value of strain (0.38%) and dynamic strain (d(33)* = 542 p.m./V) under the field 70 kV/cm.