IMF2017

Lead-free piezoelectric ceramics 1-x(Bi_0.5Na_0.5TiO₃)-xBaTiO₃ where x = 0.055, 0.06 and 0.07 (i.e., near the morphotropic phase boundary) were prepared with modified A-site cation stoichiometry to induce acceptor (excess Na) and donor (excess Bi) doping. Donor doping had no effects on the crystal structure while acceptor doping promoted rhombohedral distortions. A significant improvement in the dielectric properties was observed in all donor-doped while a deterioration in dielectric properties was observed in all acceptor-doped compositions. Compared to the stoichiometric composition, acceptor-doped compositions exhibited all of the expected “hardening” characteristics, including a decrease in d₃₃, and tanδ , as well as an increase in mechanical quality factor (Q_m) and coercive field (E_c). The measured increase in E_c and decrease in remanent polarization (P_r) were confirmed by remanent P-E hysteresis and PUND measurements. Rietveld refinement and raman spectroscopic studies were also done in order to gain more insight on the effect of structure and symmetry on the observed hardening characteristics. The possible defect chemistry conditions responsible for the observed hardening characteristics will also be discussed.