Phase Transition Behavior and Large Piezoelectricity Near the Morphotropic Phase Boundary of Lead‐Free ( Ba 0.85 Ca 0.15 )( Zr 0.1 Ti 0.9 ) O ₃ Ceramics

The phase transition behavior and piezoelectric properties of ( Ba 1− x Ca x )( Zr 0.1 Ti 0.9 ) O 3 and ( Ba 0.85 Ca 0.15 )( Zr y Ti 1− y ) O 3 ceramics were investigated in this work to find out the potential factors contributing to large piezoelectricity. It was found that the morphotropic phase boundary ( MPB ) of ( Ba 0.85 Ca 0.15 )( Zr 0.1 Ti 0.9 ) O 3 ceramics was closely related to the presence of an intermediate phase (considered as orthorhombic phase in this work) between rhombohedral ( R ) and tetragonal ( T ) phases at a narrow region, which could be carefully adjusted by the temperature and contents of Ca and Zr in the composition. In addition, the maximum piezoelectric and electromechanical coupling coefficients (with d 33 = 572 pC/N and k p = 0.57) were observed near the MPB region close to T phase side, which might be intimately related to the presence of the intermediate phase. This investigation yielded a new sight to understand the mechanism of enhanced piezoelectricity near the MPB .