Correlation of crystal structure with the enhancement of ferroelectric and piezoelectric properties of BZT-BCT lead-free ceramics around the MPB region

Abstract

Some solid-solutions of perovskite ferroelectric oxides show excellent dielectric, ferroelectric and piezoelectric properties in the vicinity of the morphotropic phase boundary (MPB). BaTiO3 (BT) based ferroelectric materials are widely studies due to its non-toxic and nonvolatile nature. The solid-solution of (1-x) BaZr0.2Ti0.8O3- x Ba0.7Ca0.3TiO3 (BZT-BCT) around the MPB region showed the highest piezoelectric properties compared to many leadbased materials. BZT crystalizes to rhombohedral (R) crystal structure whereas BCT crystalizes to tetragonal (T) crystal structure. The composition driven phase transition from rhombohedral (R) (BZT) to tetragonal (T) (BCT) crystal structure is not a continuous one according to crystallographic point of view, so there must exist an intermediate phase. This intermediate phase is known as the MPB region around which the enhancement of the piezoelectric properties has been observed. Thus, we have planned to study systematically the changes of crystal structure from R to T phases with different concentrations of BCT in BZT matrix i.e. (1-x) BaZr0.2Ti0.8O3- x Ba0.7Ca0.3TiO3 (BZT-BCT) (x=0.3-1.0). Further, the correlation between the crystal structures of BZT-BCT around the MPB region with the enhancement of the functional properties will be studied. The dielectric, ferroelectric and piezoelectric properties have been studied which demonstrates enhanced values around the MPB region (0.5BZT-0.5BCT). The detailed study of the crystal structure and its correlation with the enhancement of functional properties will be discussed.