Origin of Fatigue in Ferroelectric Perovskite Oxides

We calculated the electronic states of ferroelectric perovskite oxides, A TiO 3 , using the discrete variational Xα cluster method. The bond order of the π bonds between Ti 3 d and O 2 p as a function of titanium ion displacement in PbTiO 3 shows a maximum. This result suggests that the magnitude of ferroelectricity is related to the magnitude of the π bonds. We also found that the occupancy of s electrons in A ions increases the strength of π bonds between a titanium ion and oxygen ions. This result also suggests that the magnitude of ferroelectricity is related to the magnitude of the π bonds. Therefore, we propose that the appearance of oxygen vacancies is one of the origins of fatigue in PZT because the π bonds between a titanium ion and oxygen ions are weakened by remaining electrons of oxygen vacancies.