Effect of La-doping on fatigue in ferroelectric perovskite oxides

We investigated the effect of La-doping on fatigue in La-doped lead zirconate titanate (PLZT), using the discrete variational X alpha cluster method. Our calculations show that the energies of the La 4f states lie between those of the O 2p states and the Ti 3d states just above the Fermi level, and also that remaining electrons prefer to occupy the La 4f states rather than the Ti 3d states. Since the origin of fatigue in lead zirconate titanate (PZT) is the occupancy of Ti 3d states by remaining electrons from oxygen vacancies, we conclude that PLZT is less susceptible to fatigue than PZT because the remaining electrons occupy the La 4f states.