Influence of A-site non-stoichiometry on structure and electrical properties of K0.5Na0.5NbO3-based lead-free piezoelectric ceramics

The coexistence zone of orthorhombic and tetragonal phases, which is dependent on non-stoichiometry, appears at −0.010 ⩽ x ⩽ 0.0125 in 0.94(K0.5+xNa0.5+x)NbO3−0.06LiNbO3 (KxNxN–6LN) ceramics. KxNxN–6LN ceramics with x = −0.0125 are of orthorhombic structure. This coexistence zone plays an important role in achieving the desired electrical properties, but an optimum range of tetragonal phase fraction exists in which the significantly enhanced piezoelectric constant d33 is attained. These findings are of importance for guiding the design of KNN-based lead-free ceramics with enhanced electrical properties.