Comparison of impact from typical additives for phase structure in (K, Na)NbO3-based ceramics

Phase engineering has been widely utilized to promote piezoelectricity in potassium sodium niobate (KNN)-based ceramics via appropriate addition. However, the different impact on phase structure from various additives is still not researched deeply. Herein, the comparison of influence on phase transition temperatures (TR-O, TO-T and TC) is emphasized on from different typically additives [Bi0.5Ag0.5ZrO3 (BAZ), BaZrO3 (BZ), and Sb5+], to reveal the intrinsic essence of structure evolution. The effect on rhombohedral-orthorhombic (R–O) phase boundary can be gained as BAZ > Sb5+>BZ because of the elevating and reducing TR-O with increasing BAZ and BZ when Sb5+ is decreased, respectively. And the influence on orthorhombic-tetragonal (O-T) phase boundary can be manifested as BAZ > Sb5+≈BZ due to the decreasing and little changed TO-T with increasing BAZ and BZ as Sb5+ is reduced, respectively. Both BAZ and BZ additives are more effective on destroying long-range ordered matrix along with lower TC and stronger relaxor behavior with respect to Sb5+, which is induced by strong local structural heterogeneity from more complex composition. Furthermore, the effect of structure evolution on electrical properties is revealed systematically. This work is beneficial to understand the rules of phase boundary formation and promote structure adjustment via component design.