Morphotropic phase boundary in (1−x)Bi0.5Na0.5TiO3–xK0.5Na0.5NbO3 lead-free piezoceramics

TLDR: In this article, the electromechanical behavior of (1−x)Bi0.5Na 0.5TiO3-xK0.4NbO3 (BNT-KNN) lead free piezoelectric ceramics is investigated for 0⩽x⩾0.12 to gain insight into the antiferroelectric-ferroelectric (AFE-FE) phase transition on the basis of the giant strain recently observed in BNT-based systems.

Abstract: The electromechanical behavior of (1−x)Bi0.5Na0.5TiO3–xK0.5Na0.5NbO3 (BNT-KNN) lead free piezoelectric ceramics is investigated for 0⩽x⩽0.12 to gain insight into the antiferroelectric-ferroelectric (AFE-FE) phase transition on the basis of the giant strain recently observed in BNT-based systems. At x≈0.07, a morphotropic phase boundary (MPB) between a rhombohedral FE phase and a tetragonal AFE phase is found. While the piezoelectric coefficient is largest at this MPB, the total strain further increases with increasing KNN content, indicating the field-induced AFE-FE transition as the main reason for the large strain.

Figures

FIG. 1. Color online a P E hysteresis of 1−x BNT-xKNN for x=0, 0.06 and 0.12, and b composition-dependent maximum and remnant polarization Pm and Pr and coercive field Ec.

FIG. 2. Color online Strain hysteresis S E of 1−x BNT-xKNN for x=0, 0.06 and 0.12 for a bipolar and b unipolar cycling, c composition dependence of strain and d piezoelectric coefficient d33, and planar coupling factor kp.