Abstract
Several mechanisms and methods have been proposed to study the nature of electric fatigue in ferroelectric materials with perovskite structure, including defect agglomeration, field screening and the reorientation of defect dipoles. To ascertain the effect of defect, defect dipoles in particular on the fatigue behavior in perovskite ferroelectrics, 0.51Pb(Lu1/2Nb1/2)O3–0.49PbTi1−xSnxO3 ferroelectric ceramics were fabricated in this work. It is found that the fatigue endurance has been enhanced after Sn-doping. An abnormal strong self-rejuvenation of polarization was also detected for un-poled and un-aged samples resulting from the reorientation of defect dipoles. The defect dipoles were determined by the confirmed change of the valence of Sn ions and the appearance of oxygen vacancies. The reorientation was also confirmed by the internal bias of P–E hysteresis loops during the fatigue process. With more Sn doped into the matrix, the symmetry changed from a coexistence of rhombohedral and tetragonal phase to a rhombohedral phase. The remnant polarization decreased, while the coercive field first decreased then increased as x increased, which resulted from the composition variance and the effect of defect dipoles. It indicates that the defect dipoles play an important role in the electric fatigue behavior of Sn-doping PLN–PT ceramics.
Highlights
Among various ferroelectrics with a complex perovskite structure, Pb(Lu1/2Nb1/2)O3–PbTiO3 (PLN–PT) solid solutions were found in which the morphotropic phase boundary (MPB) between tetragonal and rhombohedral phase is in the range of 0.49– 0.51PT, exhibiting excellent electrical properties and high Curie temperature (TC),[4,5,6] which makes the PLN–PT system a promising candidate for high-power transducer applications with a wide range of application temperature
We focus on fatigue endurance enhancement of PLN–PT ceramics and study the effect of defect dipoles on electric fatigue behavior of acceptor-doped PLN–PT ceramics. 0.51PLN–0.49PT ceramic in the MPB region close to the rhombohedral side was chosen as the matrix in this work due to the excellent electric properties of this composition
The X-ray diffractometer (XRD) patterns of 0.51Pb(Lu1/2Nb1/2)O3–0.49PbTi1ÀxSnxO3 ceramics with compositions of x 1⁄4 0–0.2 at room temperature are presented in Fig. 1(a), showing perovskite structures with x 1⁄4 0–0.12 and small amount of secondary phase compositions with x > 0.14 (the XRD pro les of which were enclosed by two dashed squares in the inset of Fig. 1(a)), which was found to be Sn2Nb2O7 and cannot be eliminated by changing synthesis conditions
Summary
Ferroelectrics with perovskite structure have been the cornerstone of modern high-tech electrical devices such as actuators, piezoelectric transducers and acoustic transducers.[1,2,3] Among various ferroelectrics with a complex perovskite structure, Pb(Lu1/2Nb1/2)O3–PbTiO3 (PLN–PT) solid solutions were found in which the morphotropic phase boundary (MPB) between tetragonal and rhombohedral phase is in the range of 0.49– 0.51PT, exhibiting excellent electrical properties and high Curie temperature (TC),[4,5,6] which makes the PLN–PT system a promising candidate for high-power transducer applications with a wide range of application temperature. E-mail: hechao@ irsm.ac.cn; lxf@ irsm.ac.cn bUniversity of Chinese Academy of Sciences, Beijing, China methods have been proposed to study the nature of electric fatigue: defect agglomeration,[14 ] eld screening resulting from surface damage,[15] local phase decomposition[16] and so on Most of these mechanisms are based on these two steps: rst, cyclic electric eld induces a creation of imperfections or a redistribution of intrinsic imperfections; second, the subsequent imperfections affect the reversible polarization.[17] Among all of the imperfections, point defects play an essential part because they affect the electric fatigue behavior signi cantly.[18,19] The existence of point defects in materials affects almost every physical property of the matrix. Ferroelectric, fatigue and dielectric characteristics of the samples with different Sn doping levels were studied, together with the chemical valence state of Sn and oxygen vacancies
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