Tetragonal Morphotropic Phase Boundary Research Articles

The Evolution of Phase, Microstructure and Electrical Properties of BZT–BCT–BLT Ceramic

(1 – x)[0.50Ba(Zr0.20Ti0.80)O3–0.50(Ba0.70Ca0.30)TiO3] – xBi0.50Li0.50TiO3 with x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 wt.% were prepared by a solid-state reaction method. The phase structure, microstructure, dielectric, ferroelectric and energy density properties of BZT–BCT–xBLT ceramics were investigated. The phase structure of the samples showed coexist phases between orthorhombic and tetragonal morphotropic phase boundary (MPB). The grain size morphology decreased with increased of x(BLT) contents. The diffuseness coefficient (γ) of ceramics are between 1.40 and 1.68, which showed the relaxor ferroelectric behavior in all the samples. The dielectric constant (εr ∼ 12,697) at 1 kHz can be improve with increased of x(BLT) = 0.02 wt.%. The highest recoverable energy-storage density (W rec= 0.069 J/cm3) with an excellent energy storage efficiency (η = 95.8%) under lower electric field of 20 kV/cm were found in the composition of x = 0.08 wt.%).

The Relationship of Phase Structure, Microstructure and Electrical Properties of BNT-BT-BST Ceramic

(0.935-x)Bi0.5Na0.5TiO3-0.065BaTiO3-xBa(Sn0.1Ti0.9O3) ceramics with x(BST) = 0, 0.01, 0.03, 0.05, 0.07, 0.10, and 0.15 wt.% were prepared by a solid-state reaction method. The phase structure, microstructure, dielectric, ferroelectric and energy storage properties analysis of BNT-BT-x(BST) ceramics were also studied. The phase structures of BNT-BT-x(BST) ceramics with difference of x(BST) contents were characterized by X-ray diffraction method (XRD). It was found that the samples showed coexistent phases between rhombohedral and tetragonal morphotropic phase boundary (MPB). The grain growth is inhibited with increase of x(BST) contents, which showed the average gain size decreased from 0.94 to 0.63 µm. The phase transition with the first anomaly temperature at the lower temperature (T FA) gradually decreased from 160 to 74 °C, and then tend to increase from 74 to 151 °C. Meanwhile, the second broad dielectric constant peak at higher temperature (T SA) tended to increase first, and then decrease from 307 to 281 °C. Both T FA and T SA exhibit an obvious dependence on the frequency, which showed the relaxor ferroelectric behavior. The highest density (ρ = 5.79 ± 0.15 g/cm3), recoverable energy storage density (W rec= 0.28 J/cm3) and energy storage efficiency (η = 53.85%) and the piezoelectric coefficient (d 33*= 450 pm/V.) was found in the composition of x(BST) = 0.05 wt.%.

Dielectric and ferroelectric properties of (Bi0.5Na0.5)0.94-δBa0.06Ti1−xNbxO3 lead-free ceramics

Lead-free ceramics (Bi0.5Na0.5)0.94-δBa0.06Ti1−xNbxO3 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were prepared via a solid-state sintering method. The ceramics exhibit pure perovskite structure as x ≤ 0.04, while the ceramic with x = 0.05 has a secondary phase. The rhombohedral (R)–tetragonal (T) morphotropic phase boundary exists in all the samples. The relative content of the T phase increases due to the Nb5+ doping. The ceramics show dense microstructures with mean grain sizes around 1–2 μm. The changes of dielectric constant and dielectric loss as a function of temperature for the unpoled and poled samples were compared. Two dielectric anomalies appear on the dielectric curves around the temperatures denoted as TRE and Tm. With the increase of Nb5+ amount, the values of TRE decrease and Tm increase. The Nb5+-doped ceramics exhibit better temperature stability of dielectric constant during a wide high-temperature window. The polarization hysteresis (P–E) loops change from typical ferroelectric loops for the sample with x = 0 to constricted P–E loops with increasing Nb5+ amount. The ceramic with x = 0.03 shows a maximum strain (Smax) of 0.55% and piezoelectric strain constant (d33*) of 675 pm/V.

Nanostructured Ceramics of Potassium Sodium Bismuth Titanate: Hydrothermal Synthesis and Piezoelectric Response at Morphotropic Phase Boundary

Potassium Sodium Bismuth Titanate (KNBT) ceramics, with the general formula (1 - x)K0.5Bi0.5TiO3 -xNa0.5Bi0.5TiO3, have been synthesized following hydrothermal route, starting with solid solutions of pure perovskite nanoceramics of KBT and NBT in desired stoichiometric weight ratios, followed by sintering between 850°C and 1000°C for few hours. Pure KNBT nanoceramics with perovskite structure, having mean particle size around 30 nm, could be obtained. Morphology of the samples is found to depend strongly on composition. A change of composition results in a phase change, as evident from X-ray structure analysis. This phase change is a result of rhombohedral to tetragonal morphotropic phase boundary (MPB) in the sample with x around 0.80. Composition dependent occurrence of MPB leads to formation of needle like structures with micrometer length scales. These are typical of tetragonal lamellar structures, suggesting partial induction of tetragonal polar order from rhombohedral structure at MPB. Dielectric and piezoelectric properties, such as dielectric constant and loss, piezoelectric coefficients and figures of merit, exhibit threshold maxima in their values at the composition corresponding to MPB. These values reported for a lead-free piezoceramic, synthesized by a comparatively simple hydrothermal route, are highly promising, and comparable to well-known PZT.

The dielectric, piezoelectric and ferroelectric properties of LaAlO3-doped Bi0.5Na0.5TiO3-BaTiO3 lead-free piezoceramics

ABSTRACTLaAlO3-doped Bi0.5Na0.5TiO3-BaTiO3(BNT-BT) lead-free piezoelectric ceramics with compositions near the rhombohedral–tetragonal morphotropic phase boundary (MPB) were prepared and investigated. The introduction of LaAlO3, which makes the ceramics samples avoid being fused, has a relatively large influence on the dielectric, piezoelectric and ferroelectric properties of BNT-BT ceramics. With the increase of doping concentration, these properties get weaker. But when the doping concentration of LaAlO3 is 0.2 mol%, the remnant polarization (Pr) and coercive field (Ec) are better than those in pure 0.93BNT-0.07BT ceramics. The ferroelectric properties of this ceramics appear an eccentric enhancement and the domain switch becomes more easily.

Thermally stable electrostrains of morphotropic 0.875NaNbO3-0.1BaTiO3-0.025CaZrO3 lead-free piezoelectric ceramics

The 0.875NaNbO3-0.1BaTiO3-0.025CaZrO3 relaxor ferroelectric ceramics were reported to exhibit thermally stable electrostrains (∼0.15% @ 6 kV/mm) from room temperature (RT) to ∼175 °C and comparable strain hysteresis (<13%) to that of typical lead-based piezoelectric ceramics. Dominant strain contribution mechanisms with increasing temperature were analyzed by means of temperature-dependent permittivity, polarization, and strain measurements and synchrotron x-ray diffraction. The rhombohedral (R) and tetragonal (T) morphotropic phase boundary provided a solid structural base for temperature-stable piezoelectric strains from RT to ∼140 °C. The growth of polar nanoregions (pseudocubic) into microdomains (R) and subsequent field-induced R-T phase transition, as well as large electrostrictive effects, sequentially contributed to high electrostrain levels in the proximity of the Curie temperature (from 140 to 175 °C). In addition, the observed low strain hysteresis was attributed to the small strain fraction from domain switching. These experimental results demonstrated that NaNbO3-based relaxor ferroelectrics might be potential lead-free materials for actuator applications.

Simultaneously enhanced ferroelectric and magnetic properties in 0.675BiFe1−x Cr x O3–0.325PbTiO3 (x = 0–0.05) ceramics

Multiferroic ceramics of 0.675BiFe1−xCrxO3–0.325PbTiO3 (x = 0, 0.01, 0.025, 0.05) were prepared and comparatively investigated. The rhombohedral–tetragonal morphotropic phase boundary (MPB) was formed in 0.675BiFeO3–0.325PbTiO3. The B-site Cr-substitution changes the structure from MPB to rhombohedral phase gradually, accompanied with monotonously decreased ferroelectric Curie temperature and average grain size. More interestingly, Such Cr-substitution enhances room temperature ferroelectric and magnetic properties simultaneously. The underlying mechanism is mainly attributed to the substitution enhanced local Fe3+–Cr3+ magnetic interaction and the suppressed oxygen vacancy effect. We believe these results are helpful supplements for optimizing structures and room temperature multiferroic properties of BiFeO3-based materials.

Enhanced electrical properties in lead-free NBT–BT ceramics by series ST substitution

Comprehensive electrical properties of 0.94(Na1/2Bi1/2)TiO3–0.06BaTiO3 lead-free ceramics by doping series SrTiO3 were investigated. High piezoelectric constant of 205pC/N and electromechanical coupling factor of 0.34 were obtained due to the forming of the rhombohedral–tetragonal morphotropic phase boundary at x=0.02–0.06. Very large recoverable strain of 0.34% was obtained at x=0.10 due to the coexistence of ferroelectric and relaxor pseudocubic phases. A large electrocaloric effect (ΔTmax=1.71K and ΔT/ΔE=0.34KmmkV−1 at 50kVcm−1) which determined by indirect measurements method was obtained at 120°C at x=0.02, which is significantly higher than that of lead-free ferroelectric ceramics reported so far. Moreover, lower operating temperatures of 50°C and 30°C were proposed when x=0.10 and 0.20 with ΔTmax=0.79K and 0.6K, respectively. These properties added together indicate a promising material for applications in cooling systems and actuators.

Processing, structure, and properties of lead-free piezoelectric NBT-BT

Lead-free piezoelectric materials have been actively studied to substitute for conventional PZT based solid solution, <TEX>$Pb(Zr_xTi_{1-x}O_3)$</TEX>, which occurs unavoidable PbO during the sintering process. Among them, Bismuth Sodium Titanate, <TEX>$Na_{0.5}Bi_{0.5}TiO_3$</TEX> (abbreviated as NBT) based solid solution is attracted for the one of excellent candidates which shows the strong ferroelectricity, Curie temperature (Tc), remnant polarization (Pr) and coercive field (Ec). Especially, the solid solution of rhombohedral phase NBT with tetragonal perovskite phase has a rhombohedral - tetragonal morphotropic phase boundary. Modified NBT with tetragonal perovskite at the region of MPB can be applied for high frequency ultrasonic application because of not only its low permittivity, high electrocoupling factor and high mechanical strength, but also effective piezoelectric activity by poling. In this study, solid state ceramic processing of NBT and modified NBT, <TEX>$(Na_{0.5}Bi_{0.5})_{0.93}Ba_{0.7}TiO_3$</TEX> (abbreviated as NBT-7BT), at the region of MPB using 7 % <TEX>$BaTiO_3$</TEX> as a tetragonal perovskite was introduced and the structure between NBT and NBT-7BT were analyzed using rietveld refinement. Also, the ferroelectric and piezoelectric properties of NBT-7BT such as permittivity, piezoelectric constant, polarization hysteresis and strain hysteresis loop were compared with those of pure NBT.

Synthesis and electrical properties of (1−x)(Na0.5Bi0.5)TiO3−xBa(Mg0.5W0.5)O3 piezoelectric ceramics

(1−x)(Na0.5Bi0.5)TiO3−xBa(Mg0.5W0.5)O3 particles with x = 0.00–0.08 were synthesized by a solvothermal approach at 230 °C for 48 h. The results of X-ray diffraction analysis revealed a rhombohedral–tetragonal morphotropic phase boundary (MPB) composition existed in the range of x = 0.05–0.06 at room temperature. The ceramics around the phase boundary composition provide excellent piezoelectric properties, i.e., the highest piezoelectric constant, d33, (108 pC/N) could be realized at x value of 0.05. By using a casting sintering method, the ceramics consisted of the oriented rod-like particles with condensed sintering body were obtained, and the piezoelectric properties could be improved to show such a high piezoelectric constant as d33 = 112 pC/N at x value of 0.05.

Sintering, Microstructure and Electrical Properties of MnO&lt;sub&gt;2&lt;/sub&gt; and CuO-Doped [Na&lt;sub&gt;0.515&lt;/sub&gt;K&lt;sub&gt;0.485&lt;/sub&gt;]&lt;sub&gt;0.94&lt;/sub&gt;Li&lt;sub&gt;0.06&lt;/sub&gt;(Nb&lt;sub&gt;0.99&lt;/sub&gt;Ta&lt;sub&gt;0.01&lt;/sub&gt;)O&lt;sub&gt;3&lt;/sub&gt; Ceramics&lt;sup&gt;&lt;/sup&gt;

Ceramics with formula (1-x-y)[Na0.515K0.485]0.94Li0.06(Nb0.99Ta0.01)O3 (NKLNT) xMnO2yCuO (when x, y = 0, 0.005 and 0.01) were prepared by a reaction sintering method. The effects of doping level on sinterability and properties of NKLNT ceramics were studied. The results indicated that the co-doping of MnO2 and CuO was effective in promoting the densification of ceramics. Grain growth during secondary recrystallization was also affected, leading to larger grain size with x, y = 0.01 sample. X-ray diffraction data showed that the orthorhombic tetragonal morphotropic phase boundary existed in all the samples. At room temperature, the dielectric properties of NKLNT ceramics were improved by doping of appropriate MnO2 and CuO content. The temperature dependence of dielectric constant showed a decrease slightly in Curie temperature (TC) with increasing MnO2 and CuO content. The composition with x = 0.005, y = 0 exhibited favorable properties for the promising lead-free piezoelectric candidate material.

Morphotropic phase boundary and electric properties in (1 − x)Bi0.5Na0.5TiO3–xBaSnO3 lead-free piezoelectric ceramics

Lead-free piezoceramics of (1 − x)Bi0.5Na0.5TiO3–xBaSnO3 (BNT–BS, x = 0, 0.02, 0.03, 0.04, 0.06, 0.09 and 0.12) have been synthesized and investigated. A rhombohedral–tetragonal morphotropic phase boundary (MPB) exists near x = 0.03. The MPB composition shows improved electrical properties: the saturated polarization, remnant polarization, coercive field, piezoelectric coefficient, planar electromechanical coupling factor, and unipolar strain are 35.8, 28.5 μC/cm2, and 4.5 kV/mm, 93 pC/N, 0.19, and 0.18 %, respectively. It is also found the introduction of BS can significantly enhance dielectric property. The structural and electrical properties are discussed by comparing with other BNT-based piezoceramics.

Structure, dielectric and ferroelectric properties of 0.92Na0.5Bi0.5TiO3–0.06BaTiO3–0.02K0.5Na0.5NbO3 lead-free ceramics: Effect of Co2O3 additive

Abstract 0.92Na 0.5 Bi 0.5 TiO 3 –0.06BaTiO 3 –0.02K 0.5 Na 0.5 NbO 3 + x wt% Co 2 O 3 (NBKT– x Co, x =0, 0.2, 0.4, 0.6, 0.8) lead-free ferroelectric ceramics were prepared via a conventional solid state reaction method. Effects of Co 2 O 3 additive on crystallite structure, microstructure, dielectric and ferroelectric properties of the NBKT– x Co ceramics were studied. X-ray diffraction results showed that the rhombohedral–tetragonal morphotropic phase boundary existed in all the ceramics, with relative amount of tetragonal phase varying with the content of Co 2 O 3 . Average grain size, maximum value of dielectric constant, Curie temperature and ferroelectric properties of the ceramics were close related to the content of Co 2 O 3 . The dielectric anomaly caused by the phase transition between the ferroelectric phase and the so-called “intermediate phase” was observed in the ceramics with x ≤0.2, while it disappeared with further increasing x . All the ceramics showed a diffuse phase transition between the “intermediate phase” and the paraelectric phase. The change in the ferroelectric properties with changing the content of Co 2 O 3 was discussed by considering the competitive effects among grain size, relative amount of the tetragonal phase and oxygen vacancies.

Crystal structure, microstructure and electrical properties of (1−x−y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiFeO3 ceramics near MPB prepared via the combustion technique

(1−x−y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiFeO3 (BNKFT-x/y with 0.12≤x≤0.24, 0≤y≤0.07) lead-free piezoelectric ceramics have been prepared by the combustion technique. The effects of amounts of x and y on structures and electrical properties were examined. Powders and ceramics can be well calcined and sintered at 750 °C for 2 h and 1025–1050 °C, respectively. The results indicated that the crystalline structure and microstructure changed with the increase of x and y concentrations. XRD results of BNKFT-x/0.03 and BNKFT-0.18/y ceramics with 0.12≤x≤0.24 and 0≤y≤0.07 showed the rhombohedral–tetragonal morphotropic phase boundary (MPB). The addition of y caused a promoted grain growth while the addition of x suppressed the grain growth. The highest density (ρ=5.85 g/cm3), superior dielectric properties at Tc (εr=7846 and tan δ=0.02), remnant polarization measured at 40 kV/cm (Pr = 20.1 μC/cm2) and piezoelectric coefficient (d33=213 pC/N) were obtained for x=0.18 and y=0.03.

DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF LEAD-FREE (Bi0.5Na0.5)0.94Ba0.06TiO3 + x%Ce2O3 + y%La2O3 + z%Y2O3 COMPOUNDS SYNTHESIZED BY SOL–GEL TECHNIQUE

( Bi 0.5 Na 0.5)0.94 Ba 0.06 TiO 3 + x% Ce 2 O 3 + y% La 2 O 3 + z% Y 2 O 3 compounds (named BNT–BT– x/y/z) were synthesized by a sol–gel technique, for (x,y,z) = (0,0,0), (0.25, 0.25, 0.25), (0.25, 0.5, 0.5), (0.5, 0.25, 0.25) and (0.5, 0.5, 0.25). The structural variation according to the different system compositions is investigated by X-ray diffraction analyses. The results shows that the addition of Ce2O3 , La2O3 or Y2O3 in BNT–BT system, do not modify the crystalline structure, and a rhombohedral–tetragonal morphotropic phase boundary is maintained for different dopant addition. The BNT–BT–x/y/z-based ceramics sintered at relatively low temperature (1100°C) exhibit a good densification ratio. The optimum dielectric and piezoelectric properties are obtained with the BNT–BT–0.5/0.25/0.25 composition. High dielectric properties at room temperature (εr &gt; 1000) and low dielectric losses (tan δ &lt; 4 × 10-2) are obtained for this composition. This compound exhibits a piezoelectric constant d33 of 95 pC/N, a good polarization behavior is observed with high remanent polarization Pr of 9.21 μC/cm2 and low value coercitive field Ec of 2.66 kV/mm.

Temperature-dependent electrical properties of B-site zinc substituted bismuth sodium titanate piezoceramics

Lead-free ceramics of B-site Zn substituted Bi0.5Na0.5TiO3, with the formula of (1−x)Bi0.5Na0.5TiO3–xBi(Zn0.5Ti0.5)O3 (BNT–BZT, x=0.01, 0.04, 0.07) have been prepared. These compositions have rhombohedral, rhombohedral–tetragonal morphotropic phase boundary, and tetragonal crystal structure, respectively. The polarization–electric field (P–E), bipolar and unipolar strain–electric field (S–E) curves of all the compositions are measured as the functions of temperature. The temperature-dependent values of the remnant polarization, maximum polarization, coercive field, bipolar and unipolar strain, as well as the shape change of P–E and S–E curves have been comparatively investigated and discussed. The observed different temperature-dependences of the above parameters are attributed to the fact that the introduction of BZN reduces the depolarization temperature and enhances relaxor characteristics, which is consistent with the temperature-dependent dielectric properties. These results are valuable in understanding and further designing noval BNT-based lead-free piezoelectric systems with high recoverable strain.

The temperature-dependent electrical properties of Bi 0.5Na 0.5TiO 3–BaTiO 3–Bi 0.5K 0.5TiO 3 near the morphotropic phase boundary

Bi 0.5Na 0.5TiO 3–BaTiO 3–Bi 0.5K 0.5TiO 3 (BNT–BT–BKT) lead-free piezoceramics with compositions near the rhombohedral–tetragonal morphotropic phase boundary (MPB) were prepared and investigated. At room temperature, all ceramics show excellent electrical properties. In this study, the best properties were observed in 0.884BNT–0.036BT–0.08BKT, with the remnant polarization, bipolar total strain, unipolar strain, piezoelectric constant, and planar electromechanical coupling factor being 34.4 μC cm −2, 0.25%, 0.15%, 122 pC N −1, and 0.30, respectively. Detailed analysis of the temperature dependence of polarization–electric field ( P– E) loops and bipolar/unipolar strain–electric field ( S– E) curves of this composition revealed a ferroelectric–antiferroelectric phase transition around 100 °C. Around this temperature, there is a significant shape change in both P– E and S– E curves, accompanied by enhanced strain and decreased polarization; the largest recoverable strain reaches 0.42%. These results can be explained by the formation of antiferroelectric order and the contribution of field-induced antiferroelectric–ferroelectric phase transition to piezoelectric response. Our results indicate that BNT–BT–BKT lead-free piezoceramics can have excellent electrical properties in compositions near the MPB and also reveal some insight into the temperature dependence of the electrical performance with the MPB composition.

Microstructure and electric properties of lead-free 0.8Bi 1/2Na 1/2TiO 3–0.2Bi 1/2K 1/2TiO 3 ceramics

The microstructure and electric properties of the rhombohedral–tetragonal morphotropic phase boundary (MPB) composition 0.8Bi 1/2Na 1/2TiO 3–0.2Bi 1/2K 1/2TiO 3 have been investigated. X-ray and electron diffraction results substantiate the co-existence of tetragonal and rhombohedral phases. The ferroelectric domains were clearly observed by electron microscopy. The oxygen octahedron tilting of the samples was studied by SAED. Both saturated polarization–electric field and butterfly shaped strain–electric field hysteresis loops prove that the MPB composition shows typical ferroelectric nature. The detailed microstructure–property characterization may shed light on the physical property of further work on BNT–BKT around morphotropic phase boundary.

Characterization of sol–gel synthesised lead-free (1 − x)Na 0.5Bi 0.5TiO 3– xBaTiO 3-based ceramics

The crystal structure, microstructure, dielectric and ferroelectric properties of (1 − x)Na 0.5Bi 0.5TiO 3– xBaTiO 3 ceramics with x = 0, 0.03, 0.05, 0.07 and 0.1 are investigated. A structural variation according to the system composition was investigated by X-ray diffraction (XRD) analyses. The results revealed that the synthesis temperature for pure perovskite phase powder prepared by the present sol–gel process is much lower (800 °C), and a rhombohedral–tetragonal morphotropic phase boundary (MPB) is found for x = 0.07 composition which showing the highest remanent polarization value and the smallest coercive field. The optimum dielectric and piezoelectric properties were found with the 0.93Na 0.5Bi 0.5TiO 3–0.07BaTiO 3 composition. The piezoelectric constant d 33 is 120 pC/N and good polarization behaviour was observed with remanent polarization ( P r) of 12.18 pC/cm 2, coercive field ( E c) of 2.11 kV/mm, and enhanced dielectric properties ɛ r > 1500 at room temperature. The 0.93Na 0.5Bi 0.5TiO 3–0.07BaTiO 3-based ceramic is a promising lead-free piezoelectric candidate for applications in different devices.

Effect of potassium concentration on the structure and electrical properties of lead-free Bi 0.5 (Na,K) 0.5 TiO 3–BiAlO 3 piezoelectric ceramics

In this study, lead-free 0.975[Bi 0.5(Na 1− x K x ) 0.5TiO 3]–0.025BiAlO 3 piezoelectric ceramics (BNKT–BA) with x ranging from 0 to 0.25 were fabricated using a conventional solid state reaction. The effects of potassium concentration ( x) on the structure and electrical properties of the ceramics were investigated. The X-ray diffraction patterns revealed that the addition of K + improved the crystal symmetry of the BNKT–BA ceramics and produced a rhombohedral–tetragonal morphotropic phase boundary (MPB) in the range of 0.15 ≤ x ≤ 0.20. The increase of the K + concentration resulted in a decreased grain growth rate and promoted the formation of grains with a cubic shape. The BNKT–BA ceramics exhibited high remanent polarizations of 25 μC/cm 2 near the rhombohedral side of the MPB composition ( x = 0.15). The polarization and strain hysteresis loops demonstrated that an increased K + concentration ( x ≥ 0.20) destabilized the ferroelectric order of the BNKT–BA ceramics, leading to degradation of the remanent polarization and coercive field. However, the destabilization of the ferroelectric order was accompanied by significant enhancements in the bipolar and unipolar strains. A large electric field-induced strain ( S = 0.33%) and a corresponding normalized strain ( d 33 * = S max / E max = 533 pm / V ) were obtained on the tetragonal side of the MPB composition ( x = 0.22).