Influence of Zn <sup>2+</sup> doping on the morphotropic phase boundary in lead‐free piezoelectric (1 – <i>x</i> )Na <sub>1/2</sub> Bi <sub>1/2</sub> TiO <sub>3</sub> ‐ <i>x</i> BaTiO <sub>3</sub>
Daniel Bremecker, K. V. Lalitha, Siegfried Teuber, Jurij Koruza, Jürgen Rödel
Abstract
Abstract A series of morphotropic phase boundary (MPB) compositions of (1– x )Na 1/2 Bi 1/2 TiO 3 ‐xBaTiO 3 ( x = 0.05, 0.055, 0.06, 0.065, 0.07), with and without 0.5 mol% Zn‐doping was synthesized using the solid‐state route. The samples were characterized using X‐ray diffraction, dielectric analysis, and electromechanical measurements (piezoelectric d 33 coefficient, coupling factor k p , mechanical quality factor Q m , and internal bias field E bias ). The increase in the ferroelectric‐relaxor transition temperature upon Zn‐doping was accompanied by a shift of the MPB toward the Na 1/2 Bi 1/2 TiO 3 ‐rich side of the phase diagram. Higher tetragonal phase fraction and increased tetragonal distortion were noted for Zn‐doped (1 – x )Na 1/2 Bi 1/2 TiO 3 ‐ x BaTiO 3 . In addition, ferroelectric hardening and the presence of an internal bias field ( E bias ) were observed for all doped compositions. The piezoelectric constant d 33 and the coupling coefficient k p decreased by up to ∼30%, while a 4‐ to 6‐fold increase in Q m was observed for the doped compositions. Apart from establishing a structure–property correlation, these results highlight the chemically induced shift of the phase diagram upon doping, which is a crucial factor in material selection for optimal performance and commercialization.