Phase transition behavior and enhanced electromechanical properties in (Ba0.85Ca0.15)(ZrxTi1−x)O3 lead-free piezoceramics

Lead-free (Ba0.85Ca0.15)(ZrxTi1−x)O3 (BCZT,0.03≤x≤0.25) ceramics were synthesized in a wide compositional range to investigate the relationship between its phase diagram and electromechanical properties. The effects of Zr content on microstructure, phase transition behavior, ferroelectric, dielectric, piezoelectric and strain properties of BCZT ceramics were systemically studied. The morphotropic phase boundary (MPB) of BCZT ceramics was closely connected with the presence of orthorhombic phase between rhombohedral and tetragonal phases at a narrow region, which could meet in a region that is termed the diffuse ferroelectric phase transition region (DPTR) in this work. As a result, the composition x=0.08 located at near MPB region close to tetragonal phase side exhibited the outstanding electrical behavior at room temperature: d33=349 pC/N, kp=43%, S=0.185% and Smax/Emax=463 pm/V. Furthermore, pure electrostrictive effect with large electrostrictive coefficient Q11 of 0.036 m4 C−2 had also been observed in the composition x=0.20, and large Q11 of MPB composition showed superior temperature stability in the investigated temperature range.