First-principle calculations of the effects of CaZrO3-doped on the structure of KNN lead-free ceramics

The electronic structure of lead-free piezoelectric ceramics (K0.5Na0.5)NbO3 and CaZrO3-modified (K0.5Na0.5) NbO3 were investigated by using first-principle calculations based on density functional theory. The calculated results show that the doping of Ca reduces the band gap and causes the Fermi surface to move toward the high-energy conduction band, and Ca more easily replaces Na than K. The doping of Zr broadens the band gap, and the Fermi surface moves toward the valence band. The doping of CaZrO3 makes it easier for KNN to be stretched from the O-phase to the T-phase, which improves the performance of KNN.