Atomic-scale insights into electronic, structural, dielectric, and ferroelectric properties of Ba(Zr, Ti)O3 perovskites

Ba(Zr, Ti)O3 perovskites are promising lead-free piezoelectric and relaxor ferroelectric materials for energy storage and harvest devices, of which the ferroelectric mechanism has long been ambiguous. We theoretically investigated the ferroelectric mechanism from the electronic and atomic scale using first-principles calculation based on density functional theory and density functional perturbation theory. With increasing zirconium con-tent, it is obtained a lattice expansion and a decrease in the ferroelectric polarization in agreement with experiment. An unstable zone-center phonon mode is observed in the polar ferroelectric phase, which tends to stabilizein the nonpolar paraelectric phase, which is associated with the engineering of the relative displacement of the B-site ions that alters the short-range force. The newly formed Ti/Zr (dzx,dyz)-O (2px,2py) pi-type bonds are discovered to be the origin of the Ba(Zr, Ti)O3ferroelectric instability and polarization. Local relaxation strains caused by lattice misalignment of the ionic displacements of Ti ions and Zr ions suppress the polarization of Ba (Zr, Ti)O3 by counteracting the off-centering of Ti ions and adjacent Zr ions in certain directions.