High-Electric-Field-Induced strain at a low driving field in lead-free 0.78Bi0.5Na0.5TiO3-0.22SrTiO3 ceramics modified with KNbO3
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Toward the development of piezoelectric actuators, single-perovskite-structure 0.78Bi0.5Na0.5TiO3-(0.22-x)SrTiO3-xKNbO3(BNT-ST-xKN, with x=0–0.03) lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method,and the effects of KN substitution on the microstructure and electrical properties were investigated. FE-SEM observationsrevealed that the grain size of the sintered specimens decreased upon KN replacement. The temperature dependence of therelative dielectric permittivity (εr–T) curves showed that the ferroelectric-to-relaxor transition temperature (TF-R) decreasedfrom 55 oC for x=0 to below room temperature for x≥0.01. The hysteresis loop became slim, with the strain initially increasingand then decreasing with an increase in the KN content. Notably, at x = 0.01, a large unipolar field-induced strain (Smax) ofup to 0.157% with corresponding normalized strain d33* (Smax/Emax) of 785 pm/V was achieved at 2 kV/mm. The high strainunder an ultra-low electric field was attributed to the local chemical inhomogeneity of the constituent elements, which wasfurther confirmed by backscattered electron (BSE) and EDX mapping analyses.
Abstract
Toward the development of piezoelectric actuators, single-perovskite-structure 0.78Bi0.5Na0.5TiO3-(0.22-x)SrTiO3-xKNbO3(BNT-ST-xKN, with x=0–0.03) lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method,and the effects of KN substitution on the microstructure and electrical properties were investigated. FE-SEM observationsrevealed that the grain size of the sintered specimens decreased upon KN replacement. The temperature dependence of therelative dielectric permittivity (εr–T) curves showed that the ferroelectric-to-relaxor transition temperature (TF-R) decreasedfrom 55 oC for x=0 to below room temperature for x≥0.01. The hysteresis loop became slim, with the strain initially increasingand then decreasing with an increase in the KN content. Notably, at x = 0.01, a large unipolar field-induced strain (Smax) ofup to 0.157% with corresponding normalized strain d33* (Smax/Emax) of 785 pm/V was achieved at 2 kV/mm. The high strainunder an ultra-low electric field was attributed to the local chemical inhomogeneity of the constituent elements, which wasfurther confirmed by backscattered electron (BSE) and EDX mapping analyses.