Decoding the Influence of Defect Dipoles on the Polarization Switching of Incommensurate Modulations of Perovskite Antiferroelectrics

Antiferroelectric systems such as Pb(Zr1−x−ySnxTiy)O3 exhibit double polarization−electric field (P−E) hysteresis loops and are interesting for actuator and dielectric energy storage applications. Here, we investigate the role of defect dipoles in influencing the polarization switching and electrostrain behavior of this antiferroelectric system. We chose a niobium (Nb)-modified composition Pb0.995(Zr0.53Sn0.40Ti0.07)0.99Nb0.01O3 and introduced defect dipoles by creating oxygen vacancies via acceptor (Fe3+) doping. We found that the remanent polarization and strain (of the field-driven ferroelectric phase) increased significantly up to a critical dopant concentration (1.2 mol %). Beyond this concentration, the polarization and strain decreased dramatically. X-ray diffraction and Raman spectroscopy techniques, however, failed to capture this nonmonotonic trend in the properties. We undertook electron paramagnetic resonance spectroscopy to explain this nonmonotonic behavior by correlating it with the nature of the defect dipoles formed in the system. We found that in the low concentration regime, oxygen vacancies are formed adjacent to the Fe-doped site, creating Fei′Zr,Sn,Ti−V0¨ dipoles. Above the critical concentration, oxygen vacancies are formed at larger distances from the Fe-doped sites. Our study confirms that Fei′Zr,Sn,Ti−V0¨ defect dipoles help in significantly increasing the polarization switching and electrostrain of this system. Beyond the critical concentration, the dopant increases structural disorder and reduces the overall polarization. The understanding developed here can be used to explain the effect of defect dipoles in influencing the polarization switching behavior of antiferroelectric systems.