Abstract

Doping strongly influences the properties of ferroelectric perovskite materials. One striking difference between donor- and acceptor-doped materials is the transition from "soft" to "hard" ferroelectric behavior. The physical reasons for this phenomenon are still unclear. The authors present measurements of the ferroelectric hysteresis and deaging behavior of iron-doped lead zirconate titanate after adjusting the defect structure by heat treatment in an oxygen-depleted atmosphere. Contrary to expectations, the introduction of extra oxygen vacancies makes the material "softer." This effect, which is discussed based on a model of defect dipoles, sheds new light on the unsolved problem of hardening and aging.