Forced electrostriction by constraining polarization switching enhances the electromechanical strain properties of incipient piezoceramics

Abstract

Recently developed lead-free incipient piezoceramics are promising candidates for off-resonance actuator applications due to their exceptionally large electromechanical strains. Their commercialization currently faces three critical challenges: the high driving electric field required for delivering the potentially large strains; large strain hysteresis, which is inappropriate for precision devices; and relatively high temperature dependencies. We propose that instead of utilizing incipient piezoelectric strains, harnessing the maximum possible electrostriction would provide a highly effective way to resolve all these challenges. This concept was experimentally demonstrated using textured 0.97Bi 1/2 (Na 0.78 K 0.22 ) 1/2 TiO 3 -0.03BiAlO 3 as an exemplary incipient piezoceramic, whereby texturing was achieved using a reactive templated grain-growth technique. The manufactured textured ceramic is characterized by S max /E max of 995 pm V − 1 and an electrostrictive coefficient, Q 33 , of 0.049 m 4 C − 2 . Both these parameters are as large as those of single crystals. The current work presents a significant advancement in the field of lead-free ceramics and can guide future efforts in this direction. In addition, the concept presented here can be easily transferred to other disciplines involving the design of functional properties of various materials. NPG Asia Materials (2017) 9, e346; doi:10.1038/am.2016.210; published online 27 January 2017 INTRODUCTIONSince the first report on incipient piezoelectric strain (IPS) in a (Bi 1/2 Na 1/2 )TiO 3 (BNT)-based lead-free ceramic, 1 there have been numerous attempts to enhance the strain properties of these materials. These studies have concluded that IPS is a common feature of relaxor ferroelectrics as long as their freezing temperature is below room temperature, that is, they are in the ergodic relaxor state, whereas ferroelectric long-range order is only stable under the application of a certain or higher electric field. 2-4 It should be noted that the electric-field-induced strain in a normal ferroelectric material is approximately half the strain inherently available for the given system. This result is due to the presence of the remanent state, which typically occupies~0.1% of the entire phase. 2 Piezoelectric strain commonly refers to the difference between the maximum and remanent strain levels, and it may be greatly enhanced by minimizing the remanent strain, as is the case for IPS.Thus far, most useful IPSs have been found in relaxor ferroelectrics, 3,5 indicating that the inherently large poling field, E pol , (poling field: an electric field required for inducing ferroelectric state out of the existing relaxor state, determined at the inflection point of the electric-field-dependent strain curve as illustrated

Large Piezoelectricity in Ternary Lead‐Free Single Crystals

“…In 2007, Zhang et al reported a giant electric-field induced stain in ternary (Na 0.5 Bi 0.5 )TiO 3 -BaTiO 3 -(K 0.5 Na 0.5 )NbO 3 (NBT-BT-KNN) ceramics, [22] consequently leading to a rapid surge in the research of macrostrain enhancement and microstructure understanding in bismuthalkali-based systems. [25,[30][31][32][33][34] The origin of the giant strain has been determined to be a phase transition from unclear initial state into a ferroelectric tetragonal phase (P4mm), [32] but the ground state remains controversial concerning whether it is a nonergodic relaxor with an average cubic symmetry according to the dielectric dispersion or antiferroelectric state with extremely small distortion based on its double-hysteresis polarization-field loop. [9,16,30] Either way, long range order was perlocated with rhombohedral R3c and tetragonal P4bm symmetries, as evidenced by high-resolution transmission electron microscopy.…”

Giant Field‐Induced Strain with Low Hysteresis and Boosted Energy Storage Performance under Low Electric Field in (Bi0.5Na0.5)TiO3‐Based Grain Orientation‐Controlled Ceramics

“…Apparently, in our BNT-BT-NN ceramics, the tailoring of microstructure (grain orientation) appears to have a positive effect in the production of high strain in terms of efficient domain switching from oriented grains. [34,38] Dielectric constant and loss of the random and textured ceramics depending on frequency (100 Hz-1 MHz) are compared in Figure 5a. The textured ceramics display nearly unchanged values of dielectric constant (≈1958 at 1 kHz) and loss (≈6% at 1 kHz) as compared to the random ones (≈1894 at 1 kHz and ≈5.2% at 1 kHz).…”

“…Apparently, in our BNT–BT–NN ceramics, the tailoring of microstructure (grain orientation) appears to have a positive effect in the production of high strain in terms of efficient domain switching from oriented grains. [ 34,38 ]…”

“…experimentally validated that BNT‐based RFE ceramics with the highly textured microstructure could simultaneously realize low H s and decreased E pol . [ 38 ] More importantly, the validity of constructing oriented microstructure to tailor energy storage performance was supported by a work on highly textured Pb 0.8 Ba 0.2 ZrO 3 relaxor thin film showing a large energy density along with a high thermal stability compared to the low textured counterpart. [ 43 ] To our best knowledge, thus far no experimental evidence was made with the design of an oriented microstructure to simultaneously tune the actuator and energy‐storage performance.…”

“…To enhance the piezoelectric and strain performance of piezoelectric ceramics, crystallographic texturing achieved by a templated grain growth (TGG) technique was demonstrated to be a feasible way, [9,[27][28][29][30][31][32][33][34][35][36][37] owing to the utilization of inherent anisotropy in physical properties and domain engineering. [1,38,39] Considering the situation that the hysteresis in BNT-based RFEs roots in ferroelastic domain reorientation when they undergo an electric field-driven RFE-FE transition, [40,41] one potential strategy is the optimal utilization of tailored microstructure to facilitate the filed-induced phase transition. On the other hand, in the light of the concept of TGG technique, a significantly reduced inherently poling field E pol (an electric field where the field-induced ferroelectric state out of the initial relaxor state occurs), [42] is expected in 〈00l〉 highly oriented ceramics.…”